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Directeurs adjoints Thierry FOURNIER, Klaus HASSELBACH, Serge HUANT, Laurence MAGAUD, E-enne BUSTARRET Directeur INSTITUT NEEL Capteurs thermométriques et calorimétrie Cryogénie Electronique Cristaux Massifs Op3que et Matériaux Matériaux, Rayonnements, Structure Nano-‐Op3que et Forces Nanophysique et Semiconducteurs Semi-‐conducteurs à large bande interdite • 
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Automa3sa3on et Caractérisa3on Op3que et Microscopie Instrumenta3on (X’Press) Traitement Elabora3on Matériaux Applica3ons (TEMA) •  Pôles technologiques • 
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•  Equipes de recherche Département : Physique LUmière Ma-ère (PLUM) • 
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•  Pôles technologiques Hélium : du fondamental au applica3ons Théorie de la Ma3ère Codensées Magné3sme et Supraconduc3vité Thermodynamique et biophysique des pe3ts systèmes •  Ultra-‐basses températures • 
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•  Equipes de recherche Département : Ma-ère Condensée – Basses Températures (MCBT) Cohérence quan3que Systèmes Hybrides de basse dimensionnalité Micro et NanoMagné3sme Nanospintronique et Transport Moléculaire Nano-‐Electronique Quan3que et Spectroscopies Surfaces, Interfaces et Nanostructures Théorie Quan3que des Circuits Epitaxie et couches minces Ingénierie Expérimentale Nanofab CRG et Grands Instruments • 
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ALIS (Magasin, Liquefacteur, Infrastructure, Sécurité) Administra3on Ges3on ﬁnancière Bibliothèque Centrale Informa3que SERAS Services Communs • 
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•  Pôles technologiques • 
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•  Equipes de recherche Département : électronique QUan-quE, Surfaces et spinTronique (QUEST) MASTER 1
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INSTITUT NEEL Grenoble
Proposition de stage Master 1 - Année universitaire 2016-2017
Table des matières / Contents Investigation of Second Harmonic Generation in Plasmonic Nanostructures ........................... 5
Mesure de fluctuations de vitesse par anémométrie à fibre optique .......................................... 6
Fluctuations hydrodynamique en conditions extrêmes .............................................................. 7
Turbulence Quantique : étude expérimentale............................................................................. 8
Probing the superfluid density in high temperature iron superconductors................................. 9
Etude de matériaux magnétiques à base d’élément de terre-rare et de cobalt ou fer ............... 10
Fluctuations of the Josephson current in a two-terminal Josephson junction at equilibrium...11
Systèmes Hybrides Spin-Nanorésonateurs mécaniques……………………………………...12
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Investigation of Second Harmonic Generation in Plasmonic Nanostructures
General Scope:
Nonlinear nanophotonics is a great opportunity for opening new and promising paths toward a
wide range of practical applications in sensors, quantum computers, cryptography devices... The main
challenge is to enhance non-linear response of nanosized particles in order to integrate them in optical
components. We use metallic structures because they support localised surface plasmons (LSPs) –
collective oscillations of free electrons. When excited with a laser tuned at the LSP resonance
wavelength, these structures exhibit a great near field enhancement that strongly amplifies nonlinear
processes.
Research topic and facilities available:
The main objective of this internship is to
investigate SHG in plasmonic nanostructures. SHG
is a nonlinear process in which two incident photons
are converted into a single photon at the half
wavelength. The student will perform nonlinear
optical measurements. He/she will learn up-to-date
techniques
ranging
from
ultra
sensitive
measurements to femtosecond pulse manipulation
and non-linear optical conversion. Meanwhile,
he/she will run Finite Element Method simulations
(with COMSOL) in order to compare experimental
measurements with a numerical model that has been
developed by our team. The nanoscale localization and enhancement of the electric field around the
nanostructure, the origin of the SHG or the coupling between two plasmonic nanostructures are
different aspects that can be addressed during the internship. This project will be part of a wider
research program, lead by G. Bachelier, that has been granted by the ANR. Hence, all necessary
means will be available.
Collaborations and networking: M. Ethis de Corny and G. Laurent (PhD, NOF), G. Nogues (NPSC),
G. Dantelle (OPTIMA).
Required skills: An experimentalist profile is targeted here. Though, a theoretical background in
electromagnetism, nonlinear optics and/or programming skills in MATLAB/COMSOL will be
welcome.
Starting date: As soon as possible.
Contact:
Name: Guillaume Bachelier
Institut Néel - CNRS
Phone: 04 56 38 71 46
e-mail: [email protected]
More information: http://neel.cnrs.fr
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Mesure de fluctuations de vitesse par anémométrie à fibre optique
Cadre général :
T siècle mais elle demeure un sujet
La physique de la turbulence est étudiée depuis plus d’un
ouvert. Au sein d’un écoulement turbulent, des tourbillons de tailles différentes interagissent. L’étude
de ces interactions entre structures et la compréhension des caractéristiques des très petites échelles
constitue un défi majeur qui nécessite la miniaturisation des sondes de mesure. Les capteurs doivent
être suffisamment petits pour résoudre les plus petites structures tout en étant robustes et sensibles.
Dans cet esprit, nous avons entrepris à l’Institut Néel le développement d’un anémomètre à fibre
optique. Les premiers essais ont montré que le principe de fonctionnement de la sonde est valide (voir
Figure). Un nouveau prototype est en cours de réalisation. Afin de permettre l’exploitation de la sonde,
il est maintenant important de caractériser sa réponse dans un écoulement.
Fig. [à gauche] L’écoulement arrive par la gauche et défléchit la membrane. Son déplacement est
mesuré par la fibre optique (d’après Watson et al.) [à droite] Capteur commercial à fibre (FISO).
Sujet, moyens disponibles :
Nous souhaitons recruter un étudiant en stage afin d’adapter les moyens de tests de l’Institut à l’étude
du comportement de la sonde. Pour cela, un écoulement d’air comprimé filtré sera utilisé pour
produire un signal de turbulence connu. La sonde sera montée sur une tête goniométrique. L’étudiant
devra monter le banc de test à partir de ces différents éléments et l’instrumenter. Il effectuera ensuite
une étude systématique de la réponse dynamique de la sonde en fonction de l’angle d’incidence. Le
traitement des données devra permettre de caractériser les performances de la sonde. De ce travail
dépendra la nouvelle génération de ce type de capteur.
Interactions et collaborations éventuelles :
L’anémomètre est développé au sein d’une collaboration interne à l’Institut Néel, entre des
hydrodynamiciens et des opticiens. L’étudiant sera amené a interagir pleinement avec les différents
acteurs de la collaboration. Il devra également collaborer avec les équipes techniques du laboratoire
pour les questions de mécanique.
Formation / Compétences : Compétences développées : Optique fibrée, Instrumentation,
Hydrodynamique & Turbulence, Acquisition & Traitement du signal.
Période envisagée pour le début du stage : indifférente
Contact : Chabaud Benoit, Institut Néel – CNRS/UGA, [email protected]
(contacts alternatifs : Philippe Roche, [email protected] , et Jochen Fick, [email protected] )
Site web : http://hydro.cnrs.me
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Fluctuations hydrodynamique en conditions extrêmes
Cadre général :
De tous les fluides, l’hélium cryogénique est celui
présentant la plus faible viscosité. Cette propriété est
mise à profit en laboratoire pour produire des états
turbulents très intenses, inaccessibles aux expériences
traditionnelles. L’enjeu consiste à tester les théories de
la turbulence dans des conditions optimales.
T
Les installations cryogéniques du CERN, uniques au
monde par leur puissance réfrigérante, ont permis de
construire une expérience de jet d’hélium gazeux de
tous les records, en particulier en terme d’intensité turbulente (nombre de Reynolds jusqu’à 107).
Après une première campagne de mesure ayant permis de valider l’expérience en Juillet 2015, les
prochaines campagnes sont possibles jusqu’en 2017 grâce à un financement européen.
Nous souhaitons recruter un étudiant qui participera aux futures
campagnes. Concrètement, une partie du travail sera consacrée à
l’instrumentation et à la mise en œuvre de l’expérience. L’autre partie
sera consacrée à la validation des données, et en particulier aux tests des
lois de turbulence à très haut nombre de Reynolds (statistique des
fluctuations de vitesse et de température).
L’activité est basée à Grenoble, avec des séjours courts et réguliers au
CERN.
L’expérience, coordonnée par notre laboratoire, est menée dans le cadre d’une collaboration interlaboratoires et dans le prologement de la collaboration européenne EuHit (www.euhit.org). En
particulier, le CERN héberge l’expérience principale mais des expériences de plus petites tailles seront
mises en œuvre dans notre laboratoire.
Formation / Compétences : Compétences développées: Instrumentation & Mesures bas bruit,
Hydrodynamique & Turbulence, Physique des basses températures & Cryogénie, Acquisition &
Traitement du signal.
Période envisagée pour le début du stage : indifférente. Durée minimum de 3 mois
Contact : Roche Philippe, Institut Néel – CNRS/UGA
[email protected] (04 76 88 11 52)
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Turbulence Quantique : étude expérimentale
Cadre général :
T
En dessous de 2,17 K, l’hélium liquide acquiert des
propriétés superfluides : il peut s’écouler sans viscosité et la
vorticité de son champ de vitesse devient quantifiée. On s’attend
donc à ce que sa turbulence, appelée « Turbulence Quantique »,
diffère de la turbulence « classique ».
D’après plusieurs études récentes, il semble que la principale
différence soit concentrée au niveau des plus petits tourbillons
présents dans ces 2 types de turbulence. En effet, en l’absence
d’une dissipation efficace, on s’attend à ce que les tourbillons
superfluides s’accumulent aux petites échelles de
l’écoulement.
Tube de Pitot miniaturisé
permettant la mesure de
fluctuations de vitesse superfluide
L’objectif est de détecter et comprendre cette différence, grâce à un détecteur conçu à cet effet.
Dans le cadre du stage et de la thèse, l’étudiant développera un capteur de vortex miniature (<100 µm)
en tirant profit de l’environnement grenoblois en nano-technologies (nanofab, PTA/Minatec). Ce
capteur sera ensuite exploité dans nos différents écoulements d’hélium liquide, soit superfluide soit
classique, afin de comparer les propriétés physiques des deux types de turbulence. L’un de ces
écoulements sera la soufflerie TOUPIE, spécialement construite pour répondre à cet objectif, et qui
bien vient de bénéficier d’un upgrade pour atteindre des températures approchant 1K, un record pour
une soufflerie cryogénique de grande taille.
Le projet s’inscrit dans le cadre du projet inter-laboratoires
(CEA/CNRS/ENSL/INP/UGA) SHREK (financement ANR), centré sur
une cellule d’étude de la turbulence superfluide de très grande taille
(env. 1m3). Des expériences seront aussi conçues pour cette cellule.
Tourbillons superfluides
(simulation)
Formation / Compétences développés : Hydrodynamique & Turbulence quantique, Physique des
basses températures & Cryogénie, Nanotechnologie & Technique de microfabrication, Acquisition &
Traitement du signal, Instrumentation & Mesures bas bruit
Période envisagée pour le début du stage : indifférente. Stage de 3 mois minimum
[email protected] (04 76 88 11 52) http://hydro.cnrs.me
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Probing the superfluid density in high temperature iron superconductors
Cadre général :
The mechanisms responsible for superconductivity are a central issue in contemporary physics. Very
successful models have allowed a deep understanding of these mechanisms in pure compounds and
many alloys. But the debate is completely open about the origin of superconductivity in materials with
strong electronic correlations where the electron-electron interactions are no longer negligible. Among
these systems the high temperature superconductors based on iron successfully grown recently, are
very interesting from a fundamental point of view but also possibly for future applications. From a
fundamental point of view, spin fluctuations, but also other kind of fluctuations (nematicity, orbital
order ...) could intervene for the mechanisms of this novel superconductivity [1]. Consequently, in
these systems, the link between the different electronic phases have to be clarified. The use of an
external parameter such as pressure can allow us to tune the ground state and to approach the point
where the fluctuations play an important role.
Sujet exact, moyens disponibles :As FeSe (the elementary brick of this new
superconductors) order magnetically under a pressure of 1GPa [2] we wwant
to probe its superconducting properties in measuring the magnetic penetration
depth λ and the coherence length ξ in proximity of this critical pressure.
These lengths are very fundamental and directly related to the electron
density forming the superfluid condensate but also to the superconducting
gap [3]. Moreover, the temperature dependence reflects the existence of
possible nodes in the superconducting gap, a consequences of broken
symmetry induced in the superconducting state.
We will develop and use a new experimental set-up. The candidate will have
the opportunity to interact with several collaborators at Neel institute and out
the laboratory.
[1] Fernandez & al; Nature Physics 10, 97–104 (2014) What drives nematic order in iron based superconductors?
[2] Medvedev & al; Nature Materials 8, 630 - 633 (2009) Electronic and magnetic phase diagram of FeSe with
superconductivity at 36.7 K under pressure
[3] Rodiere P & al; Phys. Rev. B 85 (2012) 214506 Scaling of the physical properties in Ba(Fe,Ni)(2)As-2 single
crystals: Evidence for quantum fluctuations
Formation / Compétences :
The candidate will have a strong background in solid state physics, electromagnetism and quantum
mechanics. We are working with an home made instrumentation developed in the laboratory, with
world-wide performances. The candidate has to be interrested by experimental development.
Période envisagée pour le début du stage :
Contact : Rodière Pierre
Institut Néel - CNRS : 04 76 88 12 70 – [email protected]
Plus d'informations sur : http://neel.cnrs.fr/spip.php?rubrique811
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Etude de matériaux magnétiques à base d’élément de terre-rare et de cobalt
ou fer
Cadre général :
Le sujet s'inscrit dans le cadre des recherches effectuées par une équipe travaillant sur les propriétés
physiques et structurales de matériaux. Nous cherchons à améliorer les propriétés des matériaux
actuels et aussi à élaborer de nouveaux composés dont il faut comprendre les propriétés fondamentales.
Les matériaux de cette famille peuvent, selon leur composition et leurs propriétés, avoir des
applications variées allant des aimants permanents utilisés dans l’électrotechnique, ou les détecteurs
aux matériaux pour l’enregistrement de haute densité ou la microélectronique moderne dite de spin.
Sujet exact, moyens disponibles :
Ce stage comporte une partie d’élaboration de ces composés, mais aussi de caractérisation de
leurs propriétés physiques. La diffraction des rayons X sera utilisée pour étudier la structure
cristalline tandis que la microscopie électronique sera mise en œuvre pour analyser la
composition chimique. Au-delà des propriétés structurales nous nous intéresserons plus
particulièrement aux propriétés magnétiques de ces matériaux à savoir : aimantation,
température d’ordre, type d’ordre magnétique retenu par le composé en fonction de l’élément
de terre rare. Ce stage est essentiellement à caractère expérimental, il sera aussi l’occasion de
manipuler divers concepts plus fondamentaux vus au cours de l’année. Les équipements
nécessaires pour mener ces recherches à l’Institut Néel sont opérationnels tant au niveau de la
synthèse que de la caractérisation des propriétés physiques.
Formation / Compétences : Le profil est celui d’un(e) étudiant(e) de Master 1 ou d’Ecole
d’Ingénieur intéressé(e) par la physique expérimentale, désireux (se) de compléter sa
formation et d’approfondir ses connaissances scientifiques et techniques en cristallographie et
magnétisme au travers d’un stage au sein d’une équipe de recherche.
Période envisagée pour le début du stage : printemps-été 2017
Contact : Isnard Olivier
Institut Néel - CNRS 04 76 88 11 46 mel [email protected]
Plus d'informations sur : http://neel.cnrs.fr
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Fluctuations of the Josephson current in a two-terminal Josephson junction
at equilibrium
Introduction : In the Josephson effect, a nondissipative
supercurrent flows through a phase-biased weak link
between two superconductors. The Josephson effect is one
of the most important building block of quantum
nanoelectronic circuits, which are the subject of intense
theoretical and experimental investigations. In our group,
we study more specifically more complex Josephson
junctions
with three or four terminals, as shown in the figure. In
general, the current is not flat in time. On the contrary it
fluctuates, for instance because of the granularity of the charge carriers, or because of a finite
temperature. The general motivation for the internship is to calculate « generalized » quantum
fluctuations of the current, which will pave the way towards a description of those junctions in terms
of density matrix theory, used routinely in atomic physics. Thus, the goal is to initiate a research
program intended to bridge between those three- or four-terminal Josephson junctions and atomic
physics.
Proposed work-program : The goal of the internship is to evaluate those generalized quantum
fluctuations of the Josephson current, starting with a two-terminal Josephson junction in the absence
of bias voltage. The method relies on analytical calculations in the framework of wave-function
calculations, similar to those studied in the M1 course of Quantum Mechanics. It will be asked to the
student to first calculate the Josephson current as a function of the phase difference, using the
proposed wave-function appproach. Thermal fluctuations of the Josephson current will next be
evaluated. The calculation of higher-order current fluctuations is also scheduled, intended to provide
evidence for a current switching at random between two opposite values.
Interactions and possible collaborations : This project is within the framework of national and
international collaborations that we have been developping over the last years. It is expected that the
student should interact on a daily basis with the other members of our group in Grenoble (Denis
Feinberg and Serge Florens), as well as with our close collaborator Benoît Douçot in Jussieu. The
student is expected to visit the experiment of François Lefloch in CEA-Grenoble. This work is also
within an on-going collaboration with the experimental group of Moty Heiblum at the Weizmann
Institute in Israël.
Required skills : It is expected that the student should master well the ideas of his M1 course on
Quantum Mechanics.
Period for the internship : Anytime during academic year 2016-2017
Contact : Régis Mélin
Institut Néel - CNRS 04-76-88-11-88, [email protected]
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Systèmes Hybrides Spin-Nanorésonateurs mécaniques
Le refroidissement et l’observation d’un oscillateur mécanique
macroscopique dans son état quantique fondamental, réalisé en
2010-2011 dans plusieurs laboratoires, permet maintenant
d’envisager la génération d’états mécaniques non-classiques.
Pour ce faire une stratégie consiste à coupler ce résonateur
mécanique ultrafroid à un autre système quantique, un qubit, dans
le but de transférer sa nature quantique à l’oscillateur. Ce faisant
on réalise un système hybride mécanique couplant les deux
briques de bases de la mécanique quantique [1,2].
Le groupe de recherche Nano-optomécanique quantique hybride de l’Institut Néel explore une voie
dans laquelle des nanofils de carbure de silicium sont couplés au spin électronique d’un centre coloré
du diamant, le centre NV (pour Nitrogen-Vacancy). Une première expérience de principe [1] a permis
de développer ce système hybride spin-oscillateur: un centre coloré hébergé dans un nanocrystal de 50
nm de diamètre a été déposé à l’extrémité d’un nanofil de SiC. En immergeant le système dans un très
fort gradient de champ magnétique, par effet Zeeman le spin du centre coloré est couplé à la position
de l’oscillateur. On a pu ainsi montrer que les vibrations de l’oscillateur sont encodées sur le spin
électronique. Ce projet vise à explorer de nouveaux mécanismes de couplage dans ces systèmes
hybrides et à étudier le couplage spin-oscillateur en sens inverse, c'est-à-dire d’encoder l’état du spin
électronique sur la position de l’oscillateur, reproduisant ainsi l’expérience de Stern et Gerlach avec
des objets macroscopiques.
Pour ce faire, une sensibilité en force extrême est requise car la force exercée par le spin sur
l’oscillateur est de l’ordre de ~20 aN pour un gradient de 1e6 T/m. De tels niveaux de sensibilité sont
accessibles avec des oscillateurs mécaniques de très faible masse, comme démontré à température
ambiante sur les nanofils de SiC [2]. De même, il est nécessaire de lire avec une grande précision les
vibrations de ces nanofils. Les travaux en cours au laboratoire démontrent que la lecture optique des
vibrations de nanofils permet de résoudre avec une grande dynamique leur mouvement Brownien.
Enfin des protocoles avancés de manipulation du spin électronique ont également été mis en œuvre [3]
au laboratoire qui ont permis de mettre en évidence la synchronisation du spin sur la vibration
mécanique [5]. On a ainsi pu observer l’analogue phononique du triplet de Mollow en
électrodynamique quantique, apparaissant lorsque le qubit de spin est fortement excité par les
vibrations du nanofil.
[1] O. Arcizet et al, Nature Physics 7, 879 (2011).
[2] A. Gloppe et al, Nature Nanotechnology (2014).
[3]S. Rohr et al., PRL 112, 010502 (2014)
[4] B. Pigeau et al, Nature Communications ( 2015).
[5] L. Mercier de Lépinay et al., arXiv:1503.03200 (2015).
Interactions et collaborations: NEEL, ENS Cachan, labo. Kastler Brossel, Uni-Basel.
Formation / Compétences : Ce sujet permettra d’acquérir un savoir-faire en nano-optique, en
nanosciences et en manipulation de système quantiques. Même si ce projet revêt un fort caractère
expérimental, l’aspect novateur des systèmes hybrides nanomécaniques requiert un intérêt poussé pour
la formalisation théorique.
Contact : Arcizet Olivier- Benjamin Pigeau, Institut Néel - CNRS : 04 76 88 12 [email protected]. Plus d'informations sur : http://neel.cnrs.fr
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MASTER 2
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Table des matières / Contents Full Quantum interference experiments using single electron charge pulses .......................... 17
Coherent mechanical driving of the spin of an individual magnetic atom with surface acoustic
waves ........................................................................................................................................ 18
Triplet photon generation in optical non linear waveguides .................................................... 19
Ultra-cold Nanomechanics ....................................................................................................... 20
Synthesis of luminescent garnet nanoparticles for white LEDs ............................................... 21
Deciphering the folding of DNA origami ................................................................................ 22
Electrodynamics of Disordered Superconductors investigated by and for Kinetic Inductance
Detectors (KIDs). ..................................................................................................................... 23
Recherche de la supraconductivité dans des bi-couches de graphène sous haute pression ..... 24
Étude de la compétition sous haute pression entre les ordres de charge et la supraconductivité
dans les cuprates de mercure à haute température critique ...................................................... 25
Highly sensitive scanning probes for nanoscale thermal microscopy...................................... 26
Visualize Unconventional Superconductivity .......................................................................... 27
Exploring Antiskyrmions ......................................................................................................... 28
Magnetic multilayers for coupled domain walls and skyrmions.............................................. 29
New generation of phosphors for LED lighting prepared by sol-gel method .......................... 30
Fluctuations hydrodynamique en conditions extrêmes ............................................................ 31
A single spin transistor for quantum processing ...................................................................... 32
Epitaxial Superconducting Quantum NanoWires .................................................................... 33
Graphene based superconducting quantum bit......................................................................... 34
Competing electronic orders in the two-dimensional limit ...................................................... 35
Large scale spin-based quantum information processing in Si28 based semiconductors ........ 36
Suspended graphene and nanotubes for low temperature opto-electronics. ............................ 37
Three-dimensional experimental study of a quantum fluid: What is the dynamic of the
quantum vortex? ....................................................................................................................... 38
Recherche de nouveaux supraconducteurs à haute température critique ................................. 39
Study of the physical properties of new unconventional superconductors under extreme
conditions of pressure............................................................................................................... 40
Glass Nanomechanical Resonators in the Quantum Ground State .......................................... 41
Fibered Nano-Optics Tweezers for Biological Applications ................................................... 42
Optical trapping for biological applications ............................................................................. 43
Evaporation in a nanoporous material: from local to collective .............................................. 44
Novel magnetic phases in frustrated fluoride compounds ....................................................... 45
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Coherent quantum phase-slips in Josephson junction chains measured in a quantum bit ....... 46
Charge detection by electrostatic force microscopy in quantum devices ................................ 47
Scanning gate microscopy on graphene quantum point contacts ............................................. 48
Résolution de nouvelles structures cristallines par Movie-Tomography en Diffraction
Electronique ............................................................................................................................. 49
Quantum Hall interferometry in high mobility Graphene ........................................................ 50
Visualizing quantum Hall edge channels in Graphene ............................................................ 51
Bio-Activation of Mesoporous Silica Nanoparticles by selective DNA destructuration ......... 52
Confined nucleation and growth of molecular nanocrystals for biophotonics and advanced
solid-state NMR ....................................................................................................................... 53
E-beam electromechanics for quantum nanomechanical engineering ..................................... 54
Electroless deposition of magnetic nanotubes and core-shell nanowires for a 3D spintronics 55
Quantum superpositions of causal relations ............................................................................. 56
New generation of phosphors for eco-efficient LED lighting: Pechini method ...................... 57
Mesure de fluctuations de vitesse par anémométrie à fibre optique ........................................ 58
Growth conditions to stabilize polar faces of ferroelectric crystals ......................................... 59
Growth of the chiral ferromagnet LiFe5O8 by high temperature flux method ........................ 60
Turbulence Quantique : étude expérimentale........................................................................... 61
Dielectric properties of the Cooper-pair insulator.................................................................... 62
Synthesis of Chiral Crystals for magnetism, spintronic and Nonlinear Optics ........................ 63
Quantum simulation in circuit-QED ........................................................................................ 64
Nouveaux matériaux magnétiques fonctionnels ...................................................................... 65
Investigation of magnetization processes in R-M intermetallic compounds ........................... 66
Development of new magnetic actuators for biology applications at the cellular scale .......... 67
Growth of ferrimagnetic spinels for spin-filtering ................................................................... 68
Scanning Josephson Tunneling Microscopy: visualizing bound states in Superconductors ... 69
Model hard-soft magnetic nanocomposites.............................................................................. 70
Plasmonic response of copper nanoparticles during their growth on TiO2 ............................. 71
Mixed order phase transition .................................................................................................... 72
Listening to the noise of a four-terminal Josephson junction .................................................. 73
Systèmes Hybrides Spin-Nanorésonateurs mécaniques ........................................................... 74
Electric field manipulation of skyrmions……………………………………………………..75
Non-equilibrium quantum modeling of nano-structure based solar cells ………………...….76
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Full Quantum interference experiments using single electron charge pulses
Context : Interference experiments are at the heart of quantum mechanics and have lead to immense
achievements over the last two decades, in particular in the field of quantum optics.
Due to the tremendous progress in nanofabrication techniques, it is now possible to isolate and
manipulate coherently single electrons, which opens the way to perform quantum optics like
experiments with electrons. Due to the fact that electrons in solids are strongly interacting particles,
new quantum entanglement schemes can be envisioned, not possible with photons.
References: Hermelin et al., Nature 477, 435-438 (2011); Yamamoto et al., Nature Nanotechnology 7,
247-251 (2012), Dubois et al. Nature 502, 659–663 (2013); Takada et al. PRL. 113, 126601 (2014)
Fig. 1. SEM image of an Aharonov-Bohm interferometer defined in a two-dimensional electron gas.
The single electrons are injected by short voltage pulses (on the left) and single shot detected with a
single charge detectors at the outputs (on the right).
Objectives: The main objective of this proposal is the unprecedented realization of a full quantum
interference experiment by manipulating and detecting electrons in a quantum conductor at the single
electron level. Full quantum operation will bring the recent field of electron quantum optics at a level
of its photonic counterpart and will be a major step in the field of Mesoscopic Quantum Physics with
possible applications to quantum information. To realize such a full quantum experiment, we will
combine our recently developed quantum interferometer with single electron sources and single
electron detectors, presently developed within the research consortium.
Possible collaboration and networking : This project is realized within a funded ANR research
collaboration between the nanoelectronics group, CEA Saclay and the theory group of CEA Grenoble.
M2 Internship susceptible to be pursued towards a PhD degree: yes (funding available)
Education / Competences: Project for Master level & Engineering degree; we are looking for a
motivated student who is interested in experiments that are challenging from the experimental as well
as theoretical point of view.
Possible period for the internship: up to 6 months in early 2016
Contact:
Christopher BAUERLE & Tristan MEUNIER
Institut Néel - CNRS: 047688 7843 e-mail: [email protected], [email protected]
For more information: http://neel.cnrs.fr
17
Coherent mechanical driving of the spin of an individual magnetic atom
with surface acoustic waves
Context: Individual spins in semiconductor nano-structures are promising for the development of
quantum information technologies. Spin based quantum systems typically rely on resonant magnetic
field to drive coherent transitions between different spin states. Although such magnetic driving has
been effective, developing alternative modes of control opens new routes for coupling disparate
quantum states to form an hybrid quantum system. Particularly useful examples are electric fields,
optical fields and mechanical lattice vibrations. The last of these represents direct spin-phonon
coupling which garner fundamental interest as a potential mediator of long-range interaction between
remote solid state spin qubits.
Detailed project and means available: Thanks to their expected long coherence time, localized
spins on individual magnetic atoms in a semiconductor host are an interesting media for storing
quantum information. The spin of an individual magnetic atom inserted in a semiconductor quantum
dot (QD) can be probed and initialized optically. Neel Institute has a long lasting experience in the
control of individual magnetic atom in semiconductors. We recently demonstrated that the spin of an
individual chromium atom (Cr) inserted in a QD can be used as an optically addressable qubit with
large intrinsic spin to strain coupling.
In this work, we will exploit the intrinsic spin to strain
coupling of Cr to perform coherent mechanical driving of
the spin of the magnetic atom. Controlled dynamical strain
will be applied on Cr-doped QDs using surface acoustic
waves (SAW). SAW, phonon-like excitations bound to the
surface of a solid, are widely used in modern electronic
devices but are also proposed as efficient quantum bus
enabling long-range coupling of a wide range of qubits.
During this internship, we will develop SAW based
devices on Cr-doped QD samples. Inter-digitated piezoelectric transducer working in the GHz range will be
designed, realized and tested. Optical measurements and comparison with a developed model will
permit to estimate the amplitude of the oscillating strain applied on individual QDs.
The next step will be to combine SAW excitation with existing resonant optical pumping technique to
probe the influence of pulsed oscillating strain on the Cr coherent dynamics. Controlling the area of
strain pulses, we will perform Rabi oscillations on the {+1;-1} Cr spin qubit (see figure). Sequences of
two π/2 pulses could be used for Ramsey types experiments for a mechanical determination of the
coherence of the {+1;-1} qubit. Our system should allow to study a single spin in the sought-after
"strong driving" regime (ΩRabi>ωqubit) and thereby shed new light on this exciting, but still underexplored area of quantum physics.
Collaboration and networking: This work, mainly experimental, will be realized in the framework
of the CEA-CNRS group «NanoPhysique et Semi-Conducteurs» (CNRS / Institut Néel & CEA /
INAC). The student will work in interaction with people in charge of the growth of samples at the
University of Tsukuba and at INAC and will have access to technology platforms (Nanofab, PTA).
He/she will be also involved in the modeling of the spin dynamics in the studied nano-structures.
This internship can be followed by a PhD thesis on the same topic.
Required profile: Master 2 (or engineering degree) with good knowledge in solid state physics
(electrical, optical and mechanical properties), quantum mechanics, optics, electronics.
Foreseen start for the internship: March 2017
Contact : Lucien BESOMBES, Institut Néel ; 04 56 38 71 58 ; lucien.besombes@grenoble .cnrs.fr
18
Triplet photon generation in optical non linear waveguides
Cadre général :
This position concerns Triple Photons Generation (TPG). It is based on a third order nonlinear optical
interaction is the most direct way to produce pure quantum states of light, called three-photons states.
These states exhibit three-body quantum entanglement and their statistics go beyond the usual
Gaussian statistics relevant to coherent sources and optical parametric twin-photon generators,
offering thus outstanding potential applications in the field of quantum information. Undoubtedly,
three-photons states are new quantum tools to study the non-intuitive properties of quantum mechanics.
In 2004, we made the first experimental demonstration of a pure TPG [Opt. Lett. 29, 2794-2796
(2004)], which means that the three photons were created from a single one, using a two-wave
stimulation scheme in a phase-matched KTiOPO4 (KTP) bulk crystal. This pioneer work has opened
new exciting opportunities in quantum optics. We made the classical and quantum theory of TPG [J.
Opt. Soc. Am. B 25(1), 98 – 102 (2008) ; Phys. Rev. A, 85(4) 02389 1-12 (2012); invited conference
at IEEE IPC San Diego 15 October 2014].
TPG was first performed in a bulk crystal, which was possible only by stimulated the process using
two modes of the field. We have then proposed a novel approach for spontaneous TPG in a guided
configuration based on a conventional glass fiber [Opt. Lett. 26(15), 3000-3002 (2011) ; Opt. Lett.,
40(6), 982 (2015) ; invited conference at Non Linear Optics, Hawaii, 27 July 2015]. TPG can benefit
from both strong confinement and long interaction length. This result is very important since it
indicates that an optical waveguide can enable to achieve a spontaneous TPG, which is completely
impossible using a bulk medium. However, because the phase matching is only possible in an optical
fiber between two different modes of propagation with a poor spatial overlap, the efficiency of TPG is
expected to be very poor (about one triplet/s in a 10 meters long fiber) The work that is proposed in
the framework of this internship is to combine the benefit of the high non linearity of bulk crystals
such as KTP and the long interaction length and the strong confinement of an optical waveguide [Opt.
Exp., 24(9), 9932(2016)]. It will be based on a ridge waveguide cut in a KTP bulk crystal (typically, a
section of 10x10 µm2 and a length of two centimeters). Prior to stimulated TPG experiments in such a
waveguide, a Third Harmonic Generation characterization has to be performed in order to test the
injection and confinement efficiency.
Interactions et collaborations éventuelles : Collaboration with : FemtoST (Besançon), Laboratoire
de Physique et Nanostructures (Marcoussis), GAP (Université de Genève).
Ce stage pourra se poursuivre par une thèse (ou ce sujet est limité à un stage M2...).PhD Possible
Formation / Compétences :A background in laser optics, non-linear optics, quantum mechanics or
quantum optics will be useful for the purpose of the project.
Période envisagée pour le début du stage : starting from february or march 2016
Contact : B. Boulanger ([email protected]), V. Boutou ([email protected])
Institut Néel - CNRS : tél : 0476887807 / 0476887410 - Plus d'informations sur : http://neel.cnrs.fr
19
Ultra-cold Nanomechanics
Context :
Keywords : quantum mechanics, nano-mechanics, non-linear phenomena, low temperatures,
ground-state cooling
Highly motivated students are sought for an ERC-funded project devoted to fundamental research
using nanomechanics cooled down to the lowest possible temperatures. It has two facets: a
macroscopic approach concerned with the quantum mechanics behavior of the moving device itself,
and a microscopic one concerned with elementary excitations in quantum matter.
Objectives and means available:
The project is based on the « brute force » cooling of nanomechanical devices down to temperatures
around/below 1 mK. For beams resonating around 100 MHz in their first flexure, the collective modes
describing the motion are in their quantum ground states. Experiments probing mechanical quantum
coherence are then possible, on a system which is at equilibrium. These coherence properties are
linked to fundamental aspects of quantum theory, with new developments (e.g. stochastic collapse)
and old paradoxes (e.g. Schrödinger cat).
Properties of quantum matter are probed by looking at intrinsic mechanical dissipation mechanisms in
the constitutive solids, or by immersing the devices in a quantum fluid: superfluid 3He. Intriguing
states of matter can then be probed, with e.g. the Tunneling Two-Level Systems of glasses and the
elementary excitations of the BCS superfluid.
These experiments rely on cryogenic capabilities of the group: dilution cryostats and nuclear
demagnetization cooling down to the 100 µK range. A new and unique platform allying microkelvin
temperatures and microwave signals is being built in our group.
Figures: a silicon-nitride high-quality nanomechanical beam coupled to a gate electrode (center), and a
microwave cavity setup for quantum-limited readout of the dynamics (right).
Possible collaboration and networking:
This research is carried out at Institut Néel, in collaboration with other researchers from the laboratory.
It is performed in the framework of the European Microkelvin Platform (EMP), with contacts to other
ultra-low temperature facilities in Europe (UK, Germany, Finland…).
Required profile:
The student should have a strong interest in fundamental research and making challenging
measurements at very low temperatures, as well as a thorough understanding of quantum theory at the
Master’s Degree level.
Ce stage pourra se poursuivre par une thèse financée
Période envisagée pour le début du stage : Flexible
Contact : Collin Eddy
Institut Néel - CNRS : 04 76 88 78 31 [email protected]
Plus d'informations sur : http://neel.cnrs.fr/spip.php?rubrique69&lang=fr
20
Synthesis of luminescent garnet nanoparticles for white LEDs
General Scope :
White LEDs are part of the new generation of lighting devices, presenting the advantages to be more
efficient in terms of energy conversion and more environmentally-friendly. They are prepared by
combining a blue-emitting GaN-diode with inorganic materials, called phosphors, emitting in the
yellow and/or red range (Figure 1a). The most commonly-used phosphors are some Y3Al5O12 crystals
doped with Ce3+ as they present a high luminescence quantum yield (over 80%). However, due to their
micrometer size, they induce scattering within the device and are responsible for light losses. In this
context, the goal of this project is to reduce the dimension of the Y3Al5O12 crystals (Figure 1b) while
preserving their high luminescence performances.
(a) (b) Blue LED λém=450 nm Micron-‐sized phosphors emitting at λém ~ 550 nm 80 nm
Figure 1: (a) Schematic of a white LED based on the combination of a blue LED and yellow
phosphors. (b) TEM image of Y3Al5O12 nano-crystals.
During this internship, we will use the solvothermal method at high pressure to prepare Y3Al5O12 and
other garnet-type nano-crystals. The goal is to control the size of the particles (between 50 and 100
nm), as well as their crystallinity and their optical properties. This internship implies the material
synthesis, their structural characterization (by x-ray diffraction, electron microscopy, dynamic light
scattering) and their optical characterization (optical spectroscopy).
All the equipment is available in the laboratory.
Interactions with the various members of the OPTIMA team at the Institut Néel
Possible collaboration with the Institut Lumière Matière (Lyon) for more advanced spectroscopy
Possible extension as a PhD:
Yes, if funding.
Required skills:
Good skills in materials science are required.
Starting date: February 2017
Contact:
Name : Géraldine Dantelle
More information : http://neel.cnrs.fr
21
Deciphering the folding of DNA origami
General Scope :
DNA nanotechnology benefits from the progresses in DNA synthesis and sequencing that permit to
use DNA as a programmable material to self-assemble algorithmically nano-objects. Our research
targets the development of molecular nanorobots that could measure and process information in
biological environment.
DNA origami pictured in Figure 1 is a class of DNA nanostructures that form programmable shapes
with sizes of the order of few 100 nm. Although the process is very robust we lack the understanding
of the folding process itself. Such understanding is crucial to foster the applications of the
methodology toward interesting applications that are foreseen in physics and medicine.
Figure 1 AFM rendering of a DNA smiley obtained by
annealing a mix a short oligo and a large genomic
DNA. The folding process still needs to be elucidated.
© Paul Rothmunds and Nick Papadakis
Figure 2 : nanocalorimetry results indicating the stable
intermediates in the folding pathway of a DNA
tetraedron
The internship proposes to study the folding pathway of model DNA nanostructures that are composed
of few synthetic strands in order to decipher the folding intermediates. One concrete of the internship
goal is to evaluate the cooperativity of the self-assembly. The student will perform nanocalorimetric
experiments, represented in Figure 2, that can identify the presence of stable intermediates in the
folding. The student will develop also the models that can first interpret the experimental data and
second explain the folding process. The internship combines experimental and modelling work.
Collaborations include groups in Bordeaux, Paris, Oxford and Tokyo.
For excellent students, an extension as a PhD is possible.
Required skills:
The student must be highly motivated by experimental work or have good programming skills.
Knowledge in biology and DNA nanotechnology is a plus but not mandatory.
Starting date: March 2017 or earlier.
Contact:
Name: GUILLOU Hervé
22
Electrodynamics of Disordered Superconductors
investigated by and for Kinetic Inductance Detectors (KIDs)
General Scope :
Kinetic Inductance Detectors (KIDs) are RLC resonators made out of superconducting
materials. They are state-of-the-art detectors for millimeter wave observations in astrophysics.
The detection principle is based on the monitoring of the resonator frequency variation
ω0=(LC)-1/2. When used as a photon detector the incident radiation breaks down Cooper
pairs, modifying the kinetic inductance L and thus the resonance frequency. The
superconducting gap △ sets in the photon detector cutoff frequency to hν>2△. In principle,
within the classic BCS-superconducting theory Tc and △ are not independent parameters as
△~1.76-2 KBTc. Thus, lowering the cutoff frequency requires to lower the working
temperature T<< Tc.
In this project we aim to develop a novel disruptive technology for light detection that are the SKID :
Sub-gap Kinetic Inductance Detectors. These detectors are sensitive to photons with an energy hν
laying well below twice the superconducting gap 2△. These detectors are innovative as they remove
the operating temperature constraint when lowering the photon detection cutoff frequency. Low
superfluid density material obtained in disorder superconductors is a key ingredient for the
development of those new detectors.
Research topic and facilities available :
NbSi-material will be investigated. Amorphous NbSi is a highly disordered superconductor.
Its normal state sheet resistance and its superconducting critical temperature Tc can be
adjusted by varying the Nb content. The student will ensure all the steps of the study from the
fabrication up to the measurements. She/he will design and nano-lithography the detectors.
Test of the detectors will be realized in an optical dilution fridge refrigerator at 100 mK.
Photo of a Kinetic Inductance Detector.
Grey: silicon substrate. White: superconducting material.
The resonator consists of a second order Hilbert shape
fractal inductor and an interdigital capacitor. The resonator
is capacitively coupled to the transmission line : top straight
line.
The project is part of the ANR ELODIS in collaboration with two others laboratory : SPSMS from
CEA Grenoble and CSNSM in Paris.
Possible extension as a PhD: yes
Required skills:
Solid state physic knowledge, taste for experimental manipulation and strong motivation.
Starting date: March or April 2017
Contact : Institut Néel - CNRS :
Florence Lévy-Bertrand, 04 76 88 12 14, [email protected]
Alessandro Monfardini, 04 76 88 10 52, [email protected]
23
Recherche de la supraconductivité dans des bi-couches de graphène sous
haute pression
Cadre général :
La multiplication des études sur le graphène a ouvert la voie vers un grand nombre des nouvelles
applications. Cependant très peu d'études expérimentales ont été réalisés sur ses propriétés
électroniques lorsque il est placé sous haute pression. Il est vrai que étant extrêmement dur dans le
plan basal, peu des changements sont attendus sur le graphène monocouche. Mais la physique des bicouches sous pression risque d'être très riche. La liaison Van-der-Waals entre deux couches de
graphène est très faible et doit être très sensible à la mise en pression. Un empilement symétrique du
type A-A forcera une liaison inter-couches entre
atomes de carbones. La bi-couche de carbone sera
déformée vers une symétrie sp3, du type diamant ou
silicène. Or des calculs théoriques récents [F. Liu et
al., Phys.Rev. Lett. 111(2013)066804] prédissent une
supraconductivité chirale dans des bi-couches de
silicène,
ainsi
que
d'autres
propriétés
supraconductrices anormales.
La transformation sous pression vers une bi-couche
"frippé" de type silicène risque d'être permanente et
irréversible, conduissant à des réelles possibilités des
nouvelles applications
Le sujet du stage consistera dans une première étape
dans la fabrication de bi-couches de graphène, déjà
mise au point dans l'Equipe HYBRIDE par V.
Bouchiat, et leur adaptation pour son montage dans les
cellules d'haute pression (déjà testée). Ensuite se feront des mesures de transport en fonction de la
température jusqu'à 1K dans des cellules de pression pouvant atteindre les 30GPa avec M. NunezRegueiro de l'Equipe MagSup, d'une grande expérience dans l'étude des composés carbonés et
supraconducteurs sous pression.
L'étudiant(e) sera amené(e) à collaborer avec des collègues des différentes équipes de l'IN.
Ce stage pourra se poursuivre par une thèse.
Une bonne connaissance de la physique de la matière condensée est souhaitée.
Contact : Nom Prénom
Nunez-Regueiro, Manuel ; [email protected] ; tél.: 0476887838
Bouchiat, Vincent ; [email protected] ; tél.: 0476881020
24
Étude de la compétition sous haute pression entre les ordres de charge et la
supraconductivité dans les cuprates de mercure à haute température
critique
Cadre général :
L'origine de la interaction responsable de la supraconductivité à haute température critique (SHTC)
continue à être un sujet extrêmement controversé. Depuis quelques années l'on a observé dans la
plupart les familles de cuprates SHTC l'existence des ordres de charge (OC) en compétition avec la
supraconductivité. Ils ont été observés dans la région sous-dopée du diagramme de phase des cuprates
SHTC en coïncidence avec le, encore incompris, pseudogap. Ce fait semblait suggérer que leur étude pourrait
apporter une nouvelle clé pour la compréhension du
problème. En particulier, il est question de déterminer si
ces ordres de OC sont intrinsèques a la physique des
SHTC. Tout récemment nous nous sommes attaqués à
l'étude des nouveaux monocristaux de haute qualité de
cuprates de mercure, ceux même dont le record de
température critique, Tc=166K à 26GPa, a été signalé par
notre laboratoire (EPL72[2005]458). Étonnement, nous
avons observé le OC sous une pression de 10GPa dans la région sur-dopée du diagramme de phase
(voir figure; soumis Science). Dans cette région, le matériau est un liquide de Fermi normal et aucune
propriété exceptionnelle, pouvant être reliée à la physique anomale des SHTC, n'est attendue. Ceci met
en question l'hypothèse de l'importance du OC pour les SHTC. Cependant, il faut faire une étude
complète des cristaux avec différents taux de dopage pour cerner clairement le comportement de ces
matériaux sous haute pression. Cette étude est le sujet de ce stage pouvant être continué en thèse.
Le candidat fera des mesures de résistance électrique sous haute pression en fonction de la température
pour déterminer l'évolution des propriétés de transport et de la supraconductivité dans de monocristaux
de cuprates de mercure Hg-1201 avec différents taux de dopage (en collaboration avec Dorothée
Colson, Service de Physique de l'État Condensé DSM/IRAMIS/SPEC, CEA Saclay). De cette manière
il pourra observer comment la concentration de porteurs affecte l'apparition du OC sous pression.
Il participera à des mesures de diffraction par rayons X réalisées à l'ESRF sous les mêmes
monocristaux en collaboration avec G. Garbarino. La corrélation entre le deux types de mesure aidera
à déceler si le OC est en effet une propriété du pseudo-gap et essentielle a la SHTC, ou un phénomène
indépendant du mécanisme de la SHTC.
Interactions et collaborations éventuelles : L'étudiant(e) sera amené(e) à collaborer avec des
collègues du laboratoire de fabrication des échantillons, ainsi qu'avec les responsables de la ligne
haute pression de l'ESRF dans le cadre des expériences de diffraction X.
Contact : Nunez-Regueiro, Manuel ; [email protected] ; tél.: 0476887838
25
Highly sensitive scanning probes for nanoscale thermal microscopy
Cadre général :
With the advancement of the understanding of heat transfer at the nanoscale, there is currently a
growing need for new experimental tools of high sensitivity to probe temperature and thermal
conductivity at low dimensions. In this respect, new instruments have to be developed to fill that
requirements. The Scanning Thermal Microscope (SThM) is one of them. This instrument consists of
using an AFM environment and a probe equipped with a highly sensitive thermometer based on NbN
developed at Néel. Using cutting edge nanotechnology processes coupled to thermal measures, our
group at Néel has acquired a unique international expertise in this direction. On a more long term, this
work will allow for the first time to extend the SThM technique to low and very low temperature
experiments.
This internship aims at (i) developing a new resistive SThM probe for nanoscale quantitative thermal
measurements, (ii) demonstrating the capabilities of the new technique on application-oriented to
micro and nanostructured materials and systems, (iii) set this new instrument for thermal
characterization at the nanoscale in an AFM environment. The major objectives of the project is to
develop complementary expertise in SThM: resistive nanothermometry, local probe instrumentation,
metrology and micro and nanofabrication. The outputs expected of the internship and then the thesis
are the successful development of this new instrument: a highly sensitive SThM working from room
temperature to very low temperature (dilution fridge); demonstration on specimens that will be
developed within the ANR consortium (especially CETHIL and IEMN) are planned.
Fig. 1 First try of fabrication of a SThM probe from an AFM tip. The resistive thermometer has four
contacts necessary for low noise measurements. The thermometer is only 100 nm large; it can be seen
in the right panel. (Institut Néel, G. Julié, J.F. Motte)
Interactions et collaborations éventuelles : this internship is a part of the ANR TIPTOP project, a 4
year R&D collaborative project with CETHIL INSA (Lyon), IEMN (Lille), and a SME CSI (Paris).
Ce stage pourra se poursuivre par une thèse (ou ce sujet est limité à un stage M2...). Yes, the
ANR project is financing a thesis scholarship from october 2017.
Formation / Compétences: the candidate has to be motivated by the development of a new highly
sensitive scientific instrument along with clean room work and innovative thermal measurements.
Période envisagée pour le début du stage : february/march 2017
Contact : Olivier BOURGEOIS
Institut Néel - CNRS : tél 334 76 88 12 17, 336 88 71 51 86 mel : [email protected]
26
Visualize Unconventional Superconductivity
General Scope
Search for manifestations of new quantum effects in unconventional superconductors by means of a
unique scanning microscope, by imaging the distribution of very small amounts of magnetic flux,
typically a hundredth of the quantized flux (h/2e) carried by a vortex in a superconductor.
Uranium based superconductors have unique properties as the extended 5f orbitals of U induce
magnetic correlations in the electronic conduction band of these materials. UPt3 is the most prominent
compound among these, the two step superconducting transition (Tc1= 0.55 K and Tc2= 0.49 K),
discovered 25 years ago in Grenoble1, makes it the unique pendant known in solid state physics of
superfluid 3He.
The unique superconducting state of UPt3 is described by a complex two component order giving rise
to three superconducting phases in the magnetic field, temperature (B,T) phase space.
The low temperature, low field phase is expected to break time reversal symmetry. In consequence an
increased vortex pinning is predicted1 at the domain boundary between domains of different chirality,
see Figure 1
40 µm
Fig. 3.) Domain walls (arrows) in superconductig
UPt3 revealed by pinning of vortices, visualized by
nanoSQUID microscopy.
Fig. 4.) NanoSQUID structured on a Si tip
(coll. IRAM/ NEEL/LPN).
During the labwork the student will systematically image vortices above the surface of high quality
single crystals of UPt3 in varying temperature, magnetic field amplitude and direction by means of our
nanoSQUID microscope operating in a dedicated dilution refrigerator.
----------------------------------1
Critical point in the superconducting phase diagram of UPt3 Hasselbach K et al.J, PRL. 1989 63 93-6.
Vortex pinning and stability in the low field, superconducting phases of UPt3, Shung E. ; Rosenbaum T. F. ;
Sigrist M. PRL. 1998 80 1078
2
The project is carried out in the framework of a longstanding collaboration with colleagues of
Néel CNRS and INAC CEA Grenoble in contact with other national and international groups.
Possible extension as a PhD: Magnetism of superconductors
Required skills: Experimental Physics, superconductivity, curiosity
Starting date: March 2017
Contact: Name: Klaus Hasselbach
Phone:04 76 88 11 54
27
Exploring Antiskyrmions
Introduction :
An antisymmetric exchange interaction, the Dzyaloshinskii-Moriya
Interaction (DMI), occurs in systems with strong spin orbit coupling
and without crystallographic inversion symmetry. The DMI
promotes perpendicular spin alignment and is the driving force for
the stabilization of exotic spin textures like skyrmions and antiskyrmions (Fig.1). These are quasi-particles characterized by chiral
vortex-like spin configurations.
Skyrmions were experimentally found in hexagonal lattices and
isolated as a metastable state. Antiskyrmions, however, were up to
now only investigated theoretically in dipolar magnets. We recently
explored the possibility to stabilize them in magnetic ultra-thin films
with DMI.
Fig1: Antiskyrmion
Project stage in Institut Néel :
We propose a fundamental pioneering work with the goal to investigate the relationship between the
crystal symmetry and the DMI symmetry in ultra-thin magnetic multilayers. Optimizing the lattice
symmetry at the interface between a magnetic layer and a heavy metal it should be possible to find the
conditions for stabilizing antiskyrmions, requiring DMI of opposite signs along different directions.
The work will be composed by different parts:
- Sample growth: Epitaxial ultra-thin layers will be grown via pulsed laser deposition in an ultra high
vacuum system. The crystal symmetry and properties will be investigated in-situ with RHEED
(Reflection High Energy Electron Diffraction) and STM (Scanning Tunneling Microscopy) and
outside the vacuum with AFM (Atomic Force Micropscopy).
- Magnetic characterization: The DMI strongly influences magnetic configurations like Domain
Walls (DW) and excitations like Spin Waves (SW). Magneto-optical techniques will thus be used to
study the DW propagation (using Kerr microscopy) and the SW symmetry (using Brillouin Light Scattering spectroscopy) -‐ Micromagnetic simulations and analytic calculations will be performed to investigate the role
of the DMI symmetry in the stabilization and in the dynamics of an isolated antiskyrmion.
Collaborations :
Imaging of magnetic textures at the nanoscale will be performed at the SOLEIL synchrotron and in
collaboration with the LPA laboratory in Montpellier. Brillouin Light Scattering to measure the DMI
anisotropy will be performed with LSPM (Villetaneuse).
Micromagnetic calculations and simulations will be developed in collaboration with the Laboratoire de
Physique des Solides (CNRS) in Orsay and Spintec in Grenoble.
Ce stage pourra se poursuivre par une thèse : Yes
Skills: This is a pioneering project, where imagination and open mind approaches are recommended.
Good mathematical skills, a fundamental knowledge of quantum physics and a good basis of
condensed matter physics are required.
Période envisagée pour le début du stage : 01/03/2017
Contact : VOGEL Jan
Institut Néel - CNRS : 0476887912
28
Magnetic multilayers for coupled domain walls and skyrmions
General Scope:
The scope of this internship is to grow and characterize magnetic multilayers in which chiral domain
walls (DW) and magnetic skyrmions may be stabilised. These multilayers, where a thin (less than 1
nm thick) Co layer is in contact with a heavy metal in a non-centrosymmetric stack, can contain chiral
magnetic textures, i.e. magnetic structures where the moment rotates from one site to the next. Such
chiral textures are induced by the interfacial Dzyaloshinskii-Moriya interaction (DMI), an antisymmetric exchange interaction, favoring a perpendicular orientation between neighboring magnetic
moments. It is in competition with the Heisenberg exchange interaction, that tends to align
neighboring spins parallel to each other. The competition between them locally induces spiraling
magnetic structures : chiral magnetic domain walls (Fig. left) and skyrmions (Fig. right). They may be
moved at high velocity using magnetic fields or electric currents. In this project, we will test
multilayer stacks containing two Co layers coupled by dipolar interactions, which will make the
domain walls and skyrmions more stable, allowing them to move at higher maximum speeds.
Research topic and facilities available:Our group has a large experience in growing and
characterizing magnetic multilayer systems. We have extensively worked on Pt/Co/AlOx and
Pt/Co/GdOx stacks. The goal of this internship will be to optimize the growth of stacks like
Pt/Co/Ir/Co/Pt with a Co thickness of 0.6 to 1.0 nm, and an Ir thickness of about 1.0 nm. These stacks
will be deposited in Institut Néel by RF sputtering. Magnetic characterization using Vibrating Sample
Magnetometry and measurements of the thickness of the different layers and the interface quality will
performed by X-ray reflectivity. Measurements of the domain wall velocities as a function of magnetic
field will be performed using Kerr microscopy. The presence of skyrmions will also be verified. After
studying the continuous layer stacks, strips some hundreds of nanometers wide and some tens of
micrometers long will be nanofabricated from these stacks. They will be used to study the propagation
of domain walls and skyrmions induced by short current pulses, which is very important for their
potential use in high density magnetic storage. All the required techniques are available at the Institut
Néel and our group Micro- and Nano-magnetism has a large experience using them.
Possible collaboration and networking:Collaboration with Laboratoire de Physique des Solides
(Orsay) for modelling static and dynamic properties of coupled domain walls and skyrmions
Possible extension as a PhD : Yes
Required skills: Good experimental skills and basic knowledge of (nano)magnetism are needed.
Starting date: 01/03/2017
Contact:
Name: Stefania Pizzini
Phone: 04 76 88 79 15
29
New generation of phosphors for LED lighting prepared by sol-gel method
General Scope: Lighting by "white LEDs" has become a major challenge for energy saving. However,
several problems need to be overcome, the most important are: cost, quality of the white
photoluminescence emission and thermal stability. Currently, all devices used, or in development,
involve rare earth ions whose main drawbacks are lighting with narrow emission bands with a
significant blue component and also their high cost as they are highly strategic elements due to the
monopoly of their production by China. At the Institut Néel, we develop a new type of phosphors
based on vitreous powders to achieve white LEDs for solid lighting. The innovative character of these
aluminum borate phosphors is to produce a broadband luminescence emission throughout the visible
spectrum, from color centers (structural defects) in an amorphous matrix. In addition, these phosphors
are made of non-toxic and abundant, no rare earth thus making them much less expensive. The project
is the pursuit of original work (thesis and patent), which has been initiated in recent years. These
phosphors are synthetized by two different “chimie douce” routes: - modified pechini method
(polymeric precursors) - sol-gel method (alkoxide precursors); each method leading to a master topic.
Research topic and facilities available: The aim of this stage are firstly: - Understanding the origin
of the emitting centers, which are related to structural defects (oxygen radicals, carbon interstitials...)
in order to optimize the luminescence properties. Recent results obtained by thermal analysis (TDATG) coupled with mass spectrometry and 13C NMR show residual carbon groups in luminescent
powders. Nevertheless, one part of the residual carbons is pyrolytic carbon (aromatic carbon), which
leads to partial re-absorption of the visible emitted luminescence, and thus induces a decrease of the
emission intensity. Furthermore, structural studies show that the interconnected inorganic network
obtained by sol-gel route retains organic moities up to high temperatures. The optimization of the
synthesis of these phosphors will be performed by sol-gel route varying chemical factors. Different
metals with lower coordination number and stoichiometric ratios of molecular precursors (allowing
metal complexation and polymerization of organic-inorganic network) will be tested. The change of
chemical composition should enable to adjust the width of the spectral emission of luminescent for
better colorimetry. A study of the different parameters of thermal treatments (heating rates, the
ranges of temperature, controlled atmosphere during treatment), which are at the origin of the
presence of emitting centers should be clarify. Finally, the understanding of the origin and role of
emitting centers and the structural characterizations and modeling of the amorphous phase will be
implemented by coupled spectroscopic studies: FTIR, UV-Vis spectroscopy, EPR, NMR, X-ray
diffraction and X-ray scattering.
Possible collaboration and networking: Institut de Recherche Chimie-Paris ; INAC-CEA Grenoble
Possible extension as a PhD: Yes
Required skills: Chemistry in solution, knowledge on physicochemical and structural
characterizations of material
Contact :
Pr Gautier-Luneau Isabelle
Institut Néel – CNRS
Phone: 04 76 88 78 04 e-mail: [email protected]/
30
Fluctuations hydrodynamique en conditions extrêmes
Cadre général :
De tous les fluides, l’hélium cryogénique est celui
présentant la plus faible viscosité. Cette propriété est
mise à profit en laboratoire pour produire des états
turbulents très intenses, inaccessibles aux expériences
traditionnelles. L’enjeu consiste à tester les théories de
la turbulence dans des conditions optimales.
T
Les installations cryogéniques du CERN, uniques au
monde par leur puissance réfrigérante, ont permis de
construire une expérience de jet d’hélium gazeux de
tous les records, en particulier en terme d’intensité turbulente (nombre de Reynolds jusqu’à 107).
Après une première campagne de mesure ayant permis de valider l’expérience en Juillet 2015, les
prochaines campagnes sont possibles jusqu’en 2017 grâce à un financement européen.
Nous souhaitons recruter un étudiant (stage + thèse) qui participera aux
futures campagnes et conduira l’analyse physique des données
turbulentes. Concrètement, une partie du travail sera consacrée à
l’instrumentation et à la mise en œuvre de l’expérience. L’autre partie
sera consacrée à l’analyse des données, et en particulier aux tests des
lois de turbulence à très haut nombre de Reynolds (statistique des
fluctuations de vitesse et de température). Des mesures complémentaires
seront menées dans d’autres écoulements d’hélium, disponibles à
Grenoble.
L’activité est basée à Grenoble, avec des séjours courts et réguliers au CERN.
L’expérience, coordonnée par notre laboratoire, est menée dans le cadre d’une collaboration interlaboratoires et dans le prologement de la collaboration européenne EuHit (www.euhit.org). En
particulier, le CERN héberge l’expérience principale mais des expériences de plus petites tailles seront
mises en œuvre dans notre laboratoire.
Ce stage pourra se poursuivre par une thèse : Oui
Formation / Compétences : Compétences développées: Instrumentation & Mesures bas bruit,
Hydrodynamique & Turbulence, Physique des basses températures & Cryogénie, Nanotechnologie &
Technique de microfabrication, Acquisition & Traitement du signal.
[email protected] (04 76 88 11 52)
http://hydro.cnrs.me
31
A single spin transistor for quantum processing
Cadre général :
The realization of an operational quantum computer is one of the
most ambitious technological goals of today’s scientists. In this
regard, the basic building block is generally composed of a twolevel quantum system (a quantum bit). It must be fully
controllable and measurable, which requires a connection to the
macroscopic world. In this context, solid state devices, which
establish electrical connections to the qubit are of high interest.
Among the different solid state concepts, spin based devices are
very attractive since they already exhibit long coherence times.
Electrons possessing a spin 1/2 are conventionally thought as the natural carriers of quantum
information, but alternative concepts make use of the outstanding properties of molecular magnets as
building blocks for nanospintronics devices and quantum computing. Their magnetic moment, or the
nuclear spin carried by a single atom, benefit from longer coherence times compared to purely
electronic spins. In this context, our team combines the different disciplines of spintronics, molecular
electronics, and quantum information processing. In particular, we fabricate, characterize and study
molecular spin-transistor in order to manipulate[1] and read-out an individual spin[2] to perform
quantum operations.
[1] S. Thiele, F. Balestro, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Science 2014.
[2] R. Vincent, S. Klyatskaya, M. Ruben, W. Wernsdorfer, F. Balestro. Nature 2012.
Nano-devices addressing single molecular spins will be designed and reliable methods for their
realization and caracterization will be developed. Our team has a strong experience in molecular
magnetism, nanofabrication, ultra-low noise transport measurements, microwave electronics and
cryogenic equipment. First, the student will learn and participate to the sample fabrication using the
clean room facilities of the Néel Institut. She/he will then carry out the measurements of the device at
very low temperature (20mK), using one of the six fully equipped dilution refrigerators of the team, in
order to create, characterize and manipulate single spin using spin based molecular quantum dot.
This multidisciplinary research field is based on years of collaborations with teams from different
scientific and technical cultures (cleanroom, technicians, collaborations with chemists and
theoreticians, ...), in the framework of European projects and different national and regional funding.
Formation / Compétences : M2 level
We are looking for a motivated student who is interested in experiments that are challenging from the
experimental point of view.
Période envisagée pour le début du stage : from Feb 1st up to 5-6 months
Contact : BALESTRO Franck
Institut Néel - CNRS : [email protected]
For more information : http://neel.cnrs.fr/spip.php?rubrique51
32
Epitaxial Superconducting Quantum NanoWires
Scientific Context:
During the last decade, it has been demonstrated that superconducting Josephson quantum circuits constitute
ideal blocks to build quantum bits and to realize quantum mechanical experiments. These circuits appear as
artificial atoms whose properties are fixed by electronics compounds (capacitance, inductance, tunnel
barrier)[1]. Up to now only aluminum polycrystalline films were used to realize the superconducting quantum
circuits. These films present poor structural and electrical properties (superconducting films in the dirty limit,
amorphous tunnel barrier in the Josephson junctions, amorphous native oxide…), which could limit the
quantum coherence in the experiments. High quality epitaxial thin films can overcome this limitation.
During the last years, through a collaboration
between NEEL and SIMAP (B. Gilles team), we
have successfully developed and characterized
very high quality epitaxial superconducting films
of rhenium. These films present very low density
of defects and impurities leading, as example, to
very long mean free path for the electrons and to
the absence of native oxide[2]. This opens new
possibilities to build superconducting quantum
circuits based on nanowires. In our team we have
developed original microwave quantum optics
experiments coupling artificial atoms and
microwave resonators[1] and we want to develop a
novel generation of circuits based on such high
quality material.
Figure: Epitaxial rhenium films with atomic
terraces growth by MBE in SIMAP (B. Gilles).
[1] E. Dumur et al., “V-shaped superconducting artificial atom based on two inductively coupled
transmons,” Phys. Rev. B, vol. 92, no. 2, Jul. 2015.
[2] E. Dumur, et al, “Epitaxial rhenium microwave resonators”, IEEE on Applied Superconductivity, 26,
1501304, 2016.
Description, means available: The candidate will fabricate and study novel superconducting quantum nanocircuits based on epitaxial rhenium films. In particular we plan to study ultra thin films (few nanometers
thick) and superconducting nano-wires in which quantum fluctuations and nonlinearity effects could emerge.
The epitaxial films will be grown in two Molecular Beam Epitaxy equipments in SIMAP and in NEEL. The
nano-fabrication using lithography processes will be developed in NanoFab and PTA facilities. She/He will
then carry out the dc and microwave measurements of the device at very low temperature to characterize and
analyze the properties of the device. Our team has a strong experience in nanofabrication, microwave
electronics and cryogenic equipment.
Interactions and collaborations: Our team is part of several national networks. We are strongly
collaborating with Bruno Gilles in SIMAP for the epitaxial growth of rhenium thin films. This project is
financially supported by the “Agence Nationale pour la Recherche” (National French Funding Agency).
This internship can be pursued toward a PhD
Education / Profile: Master 2 or Engineering degree. We are seeking motivated students who want to
develop novel superconducting quantum circuits based on very high quality epitaxial films.
Start Period: Flexible
Contact : BUISSON Olivier and NAUD Cécile
Institut Néel- CNRS : phone: +33 4 56 38 71 77 email: [email protected], [email protected]
Plus d'informations sur : http://neel.cnrs.fr & http://neel.cnrs.fr/spip.php?rubrique50
33
Graphene based superconducting quantum bit
Cadre général :
The future of nanoelectronics will be quantum. Downscaling in electronics as now reached a point
where the size of the devices (less than 10 nm) means that their quantum behavior must be taken into
account. While this might be seen by some industries as a major problem this also gives a real
opportunity to rethink the way electronics works and make devices with new quantum functionalities.
A key building block for future quantum electronics systems is the quantum bit. Such system has two
possible states (0 and 1) but they follow the law of quantum mechanics. One example is that one might
build any superposition of 0 and 1. This will have implications for building future quantum computers.
In this work we want to build a new type of device to implement a quantum bit that we hope will have
strong advantages over other competing systems. The idea is to use the know-how that has been
developed in the superconducting quantum bit community over the past 20 years and integrate in the
core of the system a semiconducting material coupled to superconducting contacts to bring novel
electrical functionality to the device. We will use graphene, a two dimensional zero band gap
semiconductor [Nov04]. The team has a strong expertise in graphene[Ren14,Han14] that will be at the
core of this project. A sheet of graphene will have to be integrated into a superconducting quantum bit
design [Koc07] using nanofabrication techniques as illustrated in Figure 1.
Such sample will then be measured at very low temperature (20mK) in a dilution refrigerator using
radiofrequency (1-10 GHz) techniques. This will allow to demonstrate that the system behaves as a
two-level system and to show that its energy levels can be tuned with an electric field. After this
demonstration, more involved measurements will be carried out in the following PhD project (lifetime,
coherence, coherent manipulation...).
Figure 5: A Josephson
Junction, i.e. a weak link
between
two
superconducting regions, is
made
using
graphene.
Radiofrequency techniques
are used to probe the system
[Han14] Z. Han et al Nature Physics 10, 380 (2014)
[Koc07] J. Koch et al Phys. Rev. A 76, 042319 (2007)
[Nov04] K.S. Novoselov et al Science 306, 666 (2004)
[Ren14] J. Renard et al Phys. Rev. Lett. 112, 116601 (2014)
Intéractions et collaborations éventuelles : The work will be carried out in the Hybrid team. The
team has also several external collaborations worldwide (France, Germany, Canada).
Ce stage pourra se poursuivre par une thèse (ou ce sujet est limité à un stage M2...).Yes
Formation / Compétences : The internship (and the PhD thesis) will require a solid background in
solid state/condensed matter physics. The work will be mainly experimental. The candidate is
expected to be strongly motivated to learn the associated techniques (nanofabrication in clean room,
radiofrequency electronics, cryogenics...) and engage in an hands-on experimental work.
Période envisagée pour le début du stage : March 2017
Contact : Vincent Bouchiat/Julien Renard Institut Néel ; 0456387176 ; [email protected]
34
Competing electronic orders in the two-dimensional limit
Cadre général :
Tantalum disulfide (TaS2) is a lamellar material, well-known in its bulk form to condensed matter
physicists. It is prone to transformations between multiple phases, corresponding, along the z-axis, to
different atomic stacking, and in the xy-plane, to charge density waves linked to various periodic
lattice distortions. Accordingly a wealth of inter-dependent quantum states compete, from a Mott
insulator, to a metal, and a superconductor.
Recently TaS2, has been prepared in non-bulk forms, down to a single, three-atom-thick layer –
becoming a true two-dimensional (2D) material. There, not only the environment of the atoms
involved in phase transitions is qualitatively different from the bulk case, but also these atoms are all
directly amenable to scrutiny, and TaS2's electronic doping can be extensively tuned by chemical or
electrostatic gating. 2D TaS2 is thus predicted1 a unique playground to address and control a variety of
quantum phases, which started to be explored with experiments two years ago.2,3
The goal of the internship will be to prepare original architectures based on single- and few-layer
TaS2, and to address the relationship between the structure and the vibrational properties during phase
transitions, which will be induced with
changing temperature. Within the usual fewmonth duration of the internship, the scope of
the work will be on phase transitions involving
the formation of charge density waves, whose
signature will show up as specific phonon
modes and superstructure signals in diffraction
experiments. The work is meant to extend, in
the framework of a PhD thesis, to the study of
micrometer-scale devices with which nonconventional quantum phase transitions will
30 µm
be explored.
A micro-transfer facility operated under an
Figure 6: Optical image of graphene
optical microscope under a clean atmosphere
sandwiched between two hBN layers.
will be used to prepare 2D TaS2 sandwiched
between two protective thin boron nitride films, following a process established at Institut Néel for
other 2D materials (see Figure). The protected TaS2 will be studied with Raman spectro/microscopy
down to 10 K and atomic force microscopy. Other 2D TaS2 samples, prepared under ultra-high
vacuum by experts at Institut Néel, will also be studied in situ by electron diffraction down to 100 K,
by Raman spectroscopy, and scanning tunneling microscopy.
Références :
(1) A. H. Castro Neto. Charge density waves, superconductivity, and anomalous metallic behavior in 2D transition metal
dichalcogenides. Physical Review Letters Vol. 86, p. 4382 (2001)
(2) Y. Yu et al. Gate-tunable phase transitions in thin flakes of 1T-TaS2. Nature Nanotechnologies Vol. 10, p. 270 (2014)
(3) E. Navarro-Moratalla et al. Enhanced superconductivity in atomically thin TaS2. Nature Communications Vol. 7, p. 11043 (2016)
The student will join a team gathering experts in materials science, optical spectroscopy, condensed matter
physics, surface science, and first principles calculations. The proposed work is linked with several
national-scale programs, and will involve collaborations inside and outside the lab with experts in high
resolution microscopy and photoelectron spectroscopy (including at synchrotron sources).
Strong background in condensed matter physics and strong motivation for experimental work are required.
Période envisagée pour le début du stage : March 2017
Contact : Johann Coraux/ Nedjma Bendiab
Institut Néel - CNRS : [email protected]/ [email protected] d'informations
sur : http://neel.cnrs.fr
35
Large scale spin-based quantum information processing in Si28 based
semiconductors
Context : In quantum nanoelectronics, a major
goal is to use quantum mechanics in order to
build efficient nanoprocessors. This requires the
ability to control electronic phenomena in a
nanostructure at the single electron level. In this
context, the electron's spin has been identified as
an appropriate degree of freedom for efficient
storage
and
manipulation
of
quantum
information. The defined building block of this
quantum computer strategy is the spin of a single
electron trapped in a quantum dot. The
implementation of the system as a quantum
nanoprocessor resembles the classical circuit Figure: Artistic view of the sample envisioned to
boards contained in a classical computer. In dot realize a multi-dot structure to perform
systems, all the basic operations of a quantum operations and algorithms with a few electron
nanoprocessor have been demonstrated for GaAs spin qubits.
spin qubits. Intense experimental effort is
nowadays invested in Si28 semiconductor where coherence properties are the best observed for
electron spin qubits and which offers compatibility with CMOS technology used in microelectronics.
Objectives and means available : The goal of the project is to design and to measure a network of
coupled quantum dots where single spin manipulation and coherent interaction between adjacent
electron spin qubits can be implemented. The ultimate goal will be to perform small quantum
information protocols or algorithms with few spin qubits such as quantum error correction or to
displace the electron within the network. All the samples will be fabricated in CEA-LETI with a state
of the art Si facility to enable maximum output and reproductibility. To control and manipulate the
electron spin coherently, the applicant will benefit from the long-standing expertise of the Neel-group
in AlGaAs based electron spin qubits (computer control, low temperature cryogenics, low-noise
electronics, Radiofrequency electronics).
Interactions and collaborations: This work is part of a large collaborative effort between the CEAINAC, CEA-LETI and CNRS-Institut Néel to develop and push the technology of spin qubit in Si28
and investigate its potential scalability.
Skills and training : The experimental project relies on the knowledge accumulated in the field of
few-electron quantum dots and its new implementation in Si devices. All along this project, the
candidate will acquire important skills in the field of condensed matter physics: nanofabrication,
cryogenics at mK, low-noise electronics, computer control…
Foreseen start for the beginning of the internship: From January to April 2016
Possibility of continuation as a PhD on the same subject with funding already secure.
Contact : Tristan Meunier
Institut Néel/ CNRS- Université Joseph Fourier
[email protected]
plus d'information sur : http://neel.cnrs.fr
36
Suspended graphene and nanotubes for low temperature opto-electronics.
Cadre général :
Molecular electronics provides new concepts for devices with unprecedented functionalities. Due to
their low dimension, carbon nanotubes (CNTs) and graphene exhibit remarkable electronic, and
optical properties allowing the transduction of optical information into an electrical one. However,
their conductance is highly sensitive to their environment. For example grafting optically active
molecules on nanotubes realizes an optically activated transistor (1). In particular, coupling with a
substrate leads to strong modification of heat transfer, phonon lifetime, doping. We therefore suspend
graphene and nanotubes to reach a regime of low coupling with substrate phonons and charges. This is
expected to provide an optimized situation to detect small signals from molecules grafted on the
nanotube for optoelectronics at low temperature. Moreover it enables to observe out of equilibrium
regime visible both by transport and Raman spectroscopy. Such regime leads to different temperatures
of phonons and electron baths. The electron-phonon coupling plays a major role in this regime but is
not yet fully understood. It is crucial for applications to understand which coupling is involved and
whether it is dependent on the transport regime (low bias vs saturation regime).
Sujet exact, moyens disponibles:
The internship aims at investigating the out-of-equilibrium regime in
suspended nanotubes and graphene (2). To fit the timescale of the
internship, the simplest geometry will be used at room temperature: a two
laser setup will be used to heat the system while doing Raman
spectroscopy at the same point (see figure). Raman imaging will provide
information about spatial distribution of hot phonons and will allow
inferring issues on electron-phonon coupling, strain and heating in the
system (3,4). The student will be in charge of the full spectroscopic
characterization of the devices. She/He will participate to the fabrication
of the substrates and the development of the next substrates with electrical
wiring. The simultaneous use of Raman spectroscopy and electron
transport at this single nano-object level is almost unique and promising
compared to conventional methods used separately until now. The setup
in ambient conditions is fully operational. The student will participate to
the development of the 10K setup.
Figure 7: Schematic of a two
lasers experiment.
Références :
(1) Chen et al., Biologically Inspired Graphene-Chlorophyll Phototransistors with High Gain. Carbon N. Y. 63, 23 (2013).
(2) Lazzeri et al., Electron Transport and Hot Phonons in Carbon Nanotubes, Phys. Rev. Lett. 95, 236802 (2005).
(3) Cepellotti et al., Phonon hydrodynamics in two-dimensional materials. Nature Comm., 6. (2015).
(4) Balandin et al., Thermal properties of graphene and nanostructured carbon materials, Nat. Mater. 10, 569 (2011).
The student will join the Hybrid team gathering experts in materials science, optical spectroscopy,
condensed matter physics, mesoscopic transport. Close collaborations outside the lab involve material
synthesis at CIRIMAT, Toulouse, molecular synthesis at DCM, St Martin d’Hères, photoluminescence
spectroscopy at Laboratoire Pierre Aigrain, Paris. This internship can be pursued as a PhD.
A master 2 level in Condensed Matter Physics or Nanosciences is required along with motivation for
experimental work and cryogenic setup development.
Période envisagée pour le début du stage : February/March, 2017
Contact : Nedjma Bendiab, Laëtitia Marty
Institut Néel - CNRS : [email protected] / [email protected]
More information on : http://neel.cnrs.fr/spip.php?rubrique621
37
Three-dimensional experimental study of a quantum fluid:
What is the dynamic of the quantum vortex?
Cadre général :
While liquefying the most common helium isotope at a temperature
below 2.17K, a very uncommon liquid phase called HeII appears.
This phase is made of the superposition of a normal and a superfluid
that interact through mutual friction between the normal fluid and
the quantum vortices that are “carrying” the vorticity of the
superfluid. In 2006, a team of American researchers has
discovered how to trap micron-size particles on the core of these
vortices. Therefore, we can now study their dynamics using imagery
3D Lagrangian trajectories obtained by
based measurement techniques. The research project is to adapt the
LPT in a turbulent flow
three-dimensional Lagrangian Particle Tracking (3D-LPT), cutting
edge technology developed in standard fluid mechanic, to the experimental study of
these quantum vortices. I propose a series of experimental setups that will allow us to
probe the properties of quantum vortex tangles of different number density. These
experiments will help us understand the dynamic of this peculiar object together with
the interactions vortex/vortex, vortex/particle, while varying the proportion
fluid/superfluid.
We want to recruit a student (first as an intern, then as a PhD) that will acquire and
analyze the optical data mentioned above.
The internship and the first half of the PhD will be focused on the instrumentation
(temperature measurements, optical setup…) and the global setup of the experiment
(acquisition system, particle generation…). A postdoctoral research associate will help
concerning the 3D optical measurements. The second half of the PhD will be used to
refine the data analysis and the experimental protocols. In particular, the dedicated
optical cryostat will be setup on a spinning table to allow us to generate polarized
quantum vortex tangles (oriented preferentially along the axis of rotation of the system).
This project is financially supported by the ANR (“Agence Nationale de la Recherche”)
The entire work is located in Grenoble in the Institut Néel (CNRS), but collaborations
with ENS-Lyon, LEGI (Grenoble) and the Max Planck Institute for Dynamics and Selforganization (Göttingen - Germany) are planned in the context of 3D measurement
techniques and normal fluid comparison. Additionally, we expect a strong interaction
with our neighboring institute CEA/SBT.
Formation / Compétences : Physics and/or Engineering (hydro, instrumentation,
programing)
Période envisagée pour le début du stage : Indifferent
Contact : Gibert Mathieu
Institut Néel - CNRS : +33 (0)476-88-10-13 [email protected]
Plus d'informations sur : http://neel.cnrs.fr & http://www.gibert.biz
38
Recherche de nouveaux supraconducteurs à haute température critique
Cadre général :
La supraconductivité non-conventionnelle à haute température critique apparait lorsqu’un composé
bidimensionnel ayant un ordre antiferromagnétique avec une température de Néel (TN) élevé et un
faible moment magnétique est dopé. Ceci est le lié à la forte interaction d'échange, responsable de
l'antiferromagnétisme mais aussi de la supraconductivité. En particulier c'est le cas des cuprates et des
chalocgénures et arséniures de fer. Donc une stratégie raisonnable pour chercher des nouveaux
supraconducteurs non-conventionnels à haute température critique est de sélectionner des matériaux
présentant ces propriétés, les synthétiser et les doper. En particulier les composés au chrome sont
connus pour avoir un antiferromagnétisme fort. Ceux ayant en plus une basse dimensionnalité sont
difficiles à synthétiser, ce qui est un obstacle important, mais qui nous permet aussi d'être les parmi les
premiers à les étudier pour comprendre leur physique. Celle-ci peut être très riche, indépendamment
du fait de l’obtention de la supraconductivité ou non (effet Kondo Orbital dans CrSe2 [1]; Fluctuations
quantiques à 600 K dans CrRe [2].) Même s’il y a quelques années, songer à trouver de la
supraconductivité dans des composés au chrome rendait les experts sceptiques, sa découverte dans
CrAs sous pression [3], permet maintenant d’élargir ce type d'étude.
Nous proposons en premier lieu d'essayer le
dopage de composés type Ruddelsden-Popper
Æn+1CrnO3n+1 (où Æ est un alcalino-terreux;
voir figure). Nous avons déjà synthétisé les
phases mères n=1, 2 et 3, et nous avons
compris, grâce à des interactions entre
expérimentateurs et théoriciens, leur physique.
La synthèse de ces oxydes se fait à haute
pression et haute température, en profitant de
l’infrastructure très performante du laboratoire.
Les propriétés cristallographique, électrique,
magnétique, ainsi que la chaleur spécifique et
l'expansion thermique seront sondés grâces
aux différents appareils de caractérisation dont
dispose l’Institut Néel. Des mesures sous très
haute pression complèteront l’étude.
Des mesures utilisant la diffusion des neutrons (ILL) et ou des rayons X sur synchrotron (ESRF)
seront aussi nécessaires à moyen terme pour comprendre l’ensemble des propriétés. D'autre part, ce
sujet bénéficiera des interactions avec les théoriciens de l'Institut Néel ou de l'étranger.
[1] M. Núñez et al. Phys. Rev. B. 88 [2013] 245129.
[2] D. Freitas et al. Phys. Rev. B. 92 [2015] 205123.
[3] Wu Wei et al. Nature Comm.5 [2014] 5508.
Ce stage pourra se poursuivre par une thèse (ou ce sujet est limité à un stage M2...): Oui.
Période envisagée pour le début du stage : mars-avril 2017
Contact : Núñez-Regueiro, Manuel
MCBT/Institut Néel - CNRS : tél : 04 76 88 78 38 mel [email protected]
Toulemonde, Pierre
PLUM/Institut Néel - CNRS : tél : 04 76 88 74 21 mel [email protected]
39
Study of the physical properties of new unconventional superconductors
under extreme conditions of pressure
Cadre général :
The mechanism of high Tc superconductivity remains an open question in condensed matter physics.
Such superconductors show record Tc values of 135K for Cu based families and 55K for iron based
arsenides and chalcogenides at ambient pressure. The electron-phonon coupling is too weak in these
layered materials to explain their high Tc, other mechanism such as spins fluctuations has to be
involved. The comparison of the physical properties of the different families helps to find the relevant
parameters to reach high Tc superconductivity. In that sense, the use of high pressure (HP) to explore
their phase diagram is a good way to probe the physics of the parent and superconducting phases. We
actually use this approach in our laboratory to study FeSe (see fig. 1a).
More recently, we were interested in systems were Fe2Se2 unit blocks are separated by A2MO2
(Ae=Ba,Sr,Ca or K and M=Co or Cu) (see fig. 1b) because increasing distance between Fe planes
favors higher Tc. By extension we try currently to synthesize pure Fe- or pure Cu-based layered
systems with A2CuO2Cu2As2 and A2FeO2Fe2As2 compositions. An intermediate system,
Ba2Ti2Fe2As4O, where Fe2As2 layers are separated by Ti2O sheets, is also interesting because it shows
two coexisting states: superconductivity in Fe planes and a charge or spin-density wave in Ti based
sheets. During the internship, we will focus on one of these systems to characterize its physical
properties at ambient pressure and study how they change under extreme condition of pressure. In
particular we will combine structural (by x-ray diffraction in a diamond anvil cell), phonons (by
Raman spectroscopy) and transport measurements (in a diamond Bridgman anvil apparatus) under HP.
(a)
(b)
(c)
Fig.1 : (a) Pressure temperature phase diagram of FeSe (Sun et al. Nat.Comm. 7, 12146 (2016));
(b) and (c): Crystallographic structures of (Ba,K)2CuO2Fe2As2 (Dai et al. Chin. Phys. B 25, 077402 (2016)) and
Ba2Ti2Fe2As4O (Wu et al. Phys.RB 89, 134522 (2014)).
Since the discovery of superconductivity in iron-based compounds, an important knowledge of this
family has been developed in our laboratory. The candidate will benefit of it and will have the
opportunity to interact with several collaborators at NEEL Institute but also outside from Grenoble.
Ce stage pourra se poursuivre par une thèse (ou ce sujet est limité à un stage M2...) : Yes.
The candidate must have a good background in solid state physics, crystallography and material
science. In addition he has to be motivated by working with high pressure experimental setups
requiring precision and skill.
Période envisagée pour le début du stage : April 2017.
Contact : TOULEMONDE Pierre and NUNEZ-REGUEIRO Manuel
Institut Néel - CNRS :
04 76 88 74 21, [email protected];
04 76 88 78 38, [email protected]
40
Glass Nanomechanical Resonators in the Quantum Ground State
Context:
Keywords: Quantum engineering, quantum ground state, superconducting qubits, two-level
systems, glass
Highly motivated students are sought for an ERC-funded project devoted to identifying the
universal low energy excitations of glass. These excitations, thought to be two level systems (TLSs)
formed by atoms or groups of atoms tunneling between nearly equivalent states, will be probed on the
individual level for the first time. This will allow us to make a microscopic test of the controversial
“tunneling model” of glass.
Objectives and means available:
In order to access individual TLSs, a glass nanomechanical resonator will be cooled to its
quantum ground state around 1 mK. This will be achieved using a new state-of-the-art cryostat. Only
a few research groups worldwide have succeeded in cooling a mechanical resonator to the ground state,
and most of them use active cooling schemes in which only the mechanical mode of interest is cold. In
contrast, we will draw on our expertise in ultra-low temperature measurements to cool the entire
mechanical resonator to 1 mK.
Ultimately, we are interested in properties of quantum matter. In particular, the identity of the
TLSs will be investigated by making the first measurements of individual TLSs inside a mechanical
resonator. The quantum state of the resonator will be controlled using a qubit to enable these
measurements. First we will look for a signature of an individual TLS in spectroscopic measurements
of the ground-state glass resonator. Then we will use quantum control of the mechanical resonator to
in turn control and measure the quantum state of the TLS. This will yield information about the TLS
and a test of the “tunneling model” mentioned above.
Figure: Intrinsic tunneling two level systems (TLSs) inside a glass nanomechanical resonator. The mechanical
resonator will be cooled to the quantum ground state to enable measurements of the individual TLSs.
Possible collaborations and networking:
This work will involve collaboration and interactions with high profile researchers at the
Institut Néel, elsewhere in Europe and in the United States.
Required profile:
The student should have a strong interest in fundamental research and making challenging
measurements at very low temperatures, as well as a thorough understanding of quantum theory at the
Master’s Degree level.
Ce stage pourra se poursuivre par une thèse financée.
Période envisagée pour le début du stage : Flexible
Contact : Andrew Fefferman
Institut Néel - CNRS : 04.76.88.90.92 [email protected]
Plus d'informations sur : http://neel.cnrs.fr/spip.php?rubrique69&lang=fr
41
Fibered Nano-Optics Tweezers for Biological Applications
Since their introduction in 1986, optical tweezers become a standard tool for non-invasive
manipulation in biology, chemistry, and soft-mater physics. In this context we have developed an
original approach based on the use of optical fiber nano-tips, including the experimental and numerical
tools for quantifying the optical forces acting on trapped particles. Recently we have demonstrated
stable and reversible trapping of dielectric micro- and nano-particles.
A further challenge is the application of our device to biological applications. Fiber-based tweezers
have some specific advantages with respect to beam-focusing tweezers, more widely applied in biophysics: the optical fiber tips can penetrate the biological cells, the illuminated region can be limited
and more sophisticated laser beams can be used. The aim of this project are to realize force and
spectroscopic (fluorescent) measurements inside living cells and in particular for neuronal cells
(mainly neurone and astrocytes). We will investigate the mechanical and electrical signalization
pathways during cells differentiation and the feedback (impact) of the micro- environment on the
cultured cells.
The aim of the internship is to adapt and use the existing optical fiber nano-tweezers for force
measurements inside neurons. Electrical signals will also be followed by the synchronous detection
and manipulation of fluorescent voltage sensitive nano-objects along the cell membrane. The
internship is mostly experimental, but straightforward theoretical considerations will be required for
the understanding and analysis of experimental results. The student will get deeper insight into the
fields of photonics, optical forces, and biophysics.
The internship is part of a recent collaboration of two scientists both from Institut Néel but with
complementary backgrounds. Thus it will be co-supervised by Jochen Fick, specialist in photonics at
opticial trapping, and Cécile Delacour , specialist in bio-physics.
The training will take place in Institut Néels new Nano-physics-building with access to BioFap
facilities including the cell culture platform.
Required skills: The student must be highly motivated by experimental work, and should have basic
skills in optics and biophysiscs.
Starting date: as soon as possible
Contact: Jochen Fick and Cécile Delacour
e-mail: [email protected] / [email protected]
42
Optical trapping for biological applications
General Scope: Since their introduction in 1986, optical tweezers become a standard tool for noninvasive manipulation in biology, chemistry, and soft-mater physics. In this context we are developing
an optical tweezers based on strong laser beam focusing. This device will be complementary to the
optical fiber-based tweezers which was recently developed at Institut Néel. The system to develop will
allow performing fluorescence microscopy or FRET imaging in parallel to optical trapping. We aim to
develop optical tweezers, i.e. with force measurement and feedback, so as to perform force
spectroscopy on single molecules as pictured in Illustration 1. Our research in that field targets the
development of synthetic molecular machines. We focus at deciphering the folding pathway of DNAnanostructures called DNA origami that can be
algorithmically programmed to form complex shapes.
This step is crucial of ones want to self-assemble nanoobjects able to change shapes in a controlled fashion.
Research topic and facilities available: The basic part
of the optical tweezers is set-up. The aim of the internship
is to implement complementary modules (e.g. for force
measurements) and to optimize its operation. The work
includes optical trapping experiment of micro- and nanoparticles and force measurements on trapped particles.
The
internship
is
mostly
experimental,
but
straightforward theoretical considerations will also be
required for the
understanding and analysis of experimental results. The
student will get deeper insight into the fields of photonics,
Illustration 1: Representation of a single
optical forces, and spectroscopy.
molecule experiment using optical tweezers
The internship will be co-supervised by Jochen Fick, to understand the functionning of the DNAP
specialist in photonics and optical trapping, and Herve
enzyme (from Bustamante Nat. Rev 2000)
Guillou , specialist in bio-physics.
The training will take place in the new Institut Néel's BioFab facilities, with access the cell culture
platform.
Possible collaboration and networking: Ongoing collaborations include groups in Bordeaux, Paris,
Oxford, and Dijon
Possible extension as a PhD: For excellent students an extension as a PhD is possible.
Required skills: The student must be highly motivated by experimental work and have good
programming skills. Knowledges in optics and biophysics are a plus but are not required.
Contact:
Name: GUILLOU Hervé and FICK Jochen
e-mail: [email protected] / [email protected]
43
Evaporation in a nanoporous material: from local to collective
General Scope: How confinement at a nanometer scale affects condensation and evaporation of fluids
in porous materials is an active field of research. The challenge is to understand the different
microscopic processes at stake depending on connectivity and disorder of the host material, nature of
the fluid, temperature,… In this context, we use helium at cryogenic temperatures as a model fluid,
exploiting its specific properties to obtain far-reaching results. Indeed, helium offers a nearly unique
opportunity to couple high resolution thermodynamic measurements with optical observations over a
broad temperature range. The power of our approach is evidenced by results obtained in Vycor, a
disordered porous glass with a sponge topology [Europhys. Lett. 101, 16010 (2013)]. A strong light
scattering signal on evaporation is observed at low temperatures, but disappears as the temperature is
increased, suggesting an evolution from a collective to local evaporation mechanism, consistent with a
crossover from collective percolation to thermally activated cavitation. Confirming this interpretation
and understanding the conditions for this crossover is an important challenge, in particular related to
the characterization of porous materials using so-called condensation isotherms. This led us to develop
numerical simulations to analyze the optical signature of a percolation process. We predict that the
scattering signal sensitively depends on the location and density of germs. Coupling these predictions
to a phenomenological model of evaporation in a random network of pores qualitatively accounts for
our previous observations.
A disk of nanoporous Vycor in its
experimental cell, detection of
heterogeneous evaporation within the
sample, simulated microscopic distribution
of vapor for a mixed scenario
cavitation/percolation
Research topic and facilities available: The goal of this internship is to go beyond this qualitative
agreement by performing and analyzing new, dedicated, experiments in Vycor, using either cryogenic
helium or hexane or carbon dioxide at room temperature as a fluid. In both cases, the existence and
range of spatial correlations will be systematically studied by using small angle light scattering. The
intern will adapt and/or improve existing set-ups to perform small angle light scattering measurements.
He will also design and develop an automatized fluid control system. He/she will work on the optical
detection schemes, perform the experiments, and compare his/her results to our theoretical model.
Possible extension as a PhD: yes
Required skills: the candidate should have a background in condensed matter physics, with
knowledge of classical optics, and be interested by both experimental aspects and fundamental
questions. Beyond this project, the student will have opportunities to participate to our on-going
research on condensation in ordered porous materials at low temperatures.
Starting date: from January to March 2016
Contact:
Name: Panayotis Spathis / Pierre-Etienne Wolf (Institut Néel – CNRS)
E-mail: [email protected] / [email protected]
For more information: http://neel.cnrs.fr/spip.php?rubrique162 or better: drop by the lab!
44
Novel magnetic phases in frustrated fluoride compounds
Cadre général :
Geometric frustration has become a central challenge in contemporary condensed
matter physics. It arises in magnetic systems from the impossibility to minimize
AF AF simultaneously all the pair-wise exchange interactions because of constraints
imposed by the topology of the lattice (see for example Fig. 1). Some highlighted
AF results are the discovery of exotic magnetic phases, characterized by the
existence of highly degenerate ground states and the absence of conventional
long range order, such as spin-liquid phases. The spin-ice phase has especially Fig. 1: Ising spins in
retained attention: it is observed in rare earth oxides like Ho2Ti2O7 or Dy2Ti2O7, antiferromagnetic
where the spins occupy the sites of a pyrochlore network (a lattice of corner- interactions in a
sharing tetrahedra, see Fig. 2). In the spin-ice ground state, two spins point inside triangle
a tetrahedron and two spins point outside, a feature known as the “ice-rule”, in close analogy with the
proton position in water-ice. Magnetic excitations above the ground state could be identified as
magnetic monopoles [1].
Based on the extensive knowledge of these compounds, we are interested in new systems, fluorides,
with the modified pyrochlore structure AM2+M′3+F6 (where A is typically an alkali-metal ion, and M2+
and M′3+ are usually transition-metal ions, e.g., Ni2+, Cr3+). In this new
family the M2+ and M′3+ ions occupy the sites of a pyrochlore lattice but are
randomly distributed. Anderson [2] showed that minimization of the
Coulomb interaction in such a system creates a distribution of ions that
obeys the “ice rules” : each tetrahedron consists of two ions M2+ and two
ions M′3+ in arbitrary positions, thus being the realization of a “charge ice”
expected to exhibit a new type of magnetic behavior.
Fig. 2: Pyrochlore
lattice
[1] see for example Castelnovo et al. Nature 451, 42
(2008)
[2] Anderson, Phys. Rev. 102, 1008 (1956)
Preliminary measurements on three fluoride compounds (KNaCrF6, CsCoCrF6, CsMgCrF6),
synthesized at Oxford University, show the absence of long-range magnetic order down to 1.8 K,
confirming the presence of frustration and the possible existence of unconventional magnetic states.
During the internship, the magnetic properties will be measured down to very low temperature
(70 mK), using SQUID magnetometers equipped with dilution refrigerators developed at the Institut
Néel. The objective will be to determine the magnetic ground state stabilized at very low temperature
in these systems. The student will gain knowkledge of all the aspects of the experimental set-up,
including cryogenic techniques and electronics. Further measurements such as heat capacity
measurements, as well as neutron scattering and high frequency ac susceptibility with our
collaborators are also planned to get a deeper insight into the magnetism of these compounds.
Interactions et collaborations éventuelles : Collaboration with Sylvain Petit (LLB Saclay – neutron
scattering measurements) and Sean Giblin (Cardiff University, UK - high frequency susceptibility).
Formation / Compétences : Master 2 Physique
Période envisagée pour le début du stage : à partir de Janvier 2017
Contact : Lhotel Elsa
Institut Néel - CNRS : 04.75.88.12.63. , [email protected]
45
Coherent quantum phase-slips in Josephson junction chains
measured in a quantum bit
General Scope:
The Josephson effect in large Josephson junctions has given rise to celebrated applications
such as the DC and RF SQUIDs which operate as supersensitive magnetometers, single flux
quantum logic circuits and high precision Josephson voltage standards. By decreasing the
junction size of the Josephson junction, the superconducting phase undergoes quantum
fluctuations that manifest themselves in form of windings by 2π, so called quantum phaseslips. The realization of a large coherent quantum phase-slip amplitude might have possible
applications in quantum metrology.
Ebeam image of a Fluxonium qubit.
By microwave measurement techniques we would like to study the coherence of quantum
phase-slips in a circuit realizing a quantum bit configuration. We have a new dilution
refrigerator equipped with a working microwave measurement set-up enabling to do timedependent measurements of the qubit state. Further on we fabricate our samples at the
nanofabrication facility of the Néel Institute. During this internship the Master student will
learn about the theory of quantum circuits, the fabrication process and also the measurement
of a qubit.
Interactions and collaborations:
We work in close collaboration with the theoretical group of Frank Hekking and Denis Basko from
LPMMC in Grenoble. This project is funded by a grant of the European Research Council.
Possible extension as a PhD : yes
Required skills:
Master 2 or Engineering degree. We are seeking motivated students who want to take part to a state of
the art experiment and put some efforts in the theoretical understanding of quantum effects in
superconducting circuits
Starting date: 01/03/2017
Contact: Wiebke Guichard
Institut Néel - CNRS Phone : 04 56 38 70 17
46
Charge detection by electrostatic force microscopy in quantum devices
Cadre général :
Quantum point contacts (QPC) are quasi-one-dimensional channels defined by metallic gates in highmobility semiconductor heterostructures. In addition to quantized conductance plateaus, Coulomb
interactions in the channel lead to an anomalous feature below the first plateau called the “0.7
anomaly”. Despite intensive theoretical and experimental efforts during the last fifteen years, this
feature still remains unexplained. To elucidate the complex interacting electron state responsible for
this phenomenon, original experiments are necessary to provide new kind of information. We propose
to use electrostatic force microscopy (EFM) to probe the most probable but still debated scenario of a
spontaneous electron localization due the strong Coulomb interactions at low density. Combined with
another technique called scanning gate microscope (SGM), we will unambiguously verify the presence
of localized charges and answer this long-standing question on the most important quantum device.
Our scanning probe microscope uses a quartz tuning fork (TF) as force sensor and the sharp metallic
tip from a commercial EFM cantilever. The force detection limit is in principle well below a single
electron charge when the TF is at liquid helium temperature and if a cryogenic current amplifier is
integrated in-situ with the TF. We will first start these EFM experiments with quantum dots (QD)
where the Coulomb blockade phenomenon is well known, and then move to the puzzling case of QPC.
The objective of the internship will be to optimize the force sensitivity of the EFM microscope down
to a single electron charge using QD as test samples. The perspectives for a PhD thesis will be to carry
out combined EFM and SGM experiments on QPC and to develop new experiments under large
parallel magnetic field to probe the spin properties of the complex electron state in the QPC.
Sujet exact :
The master student will develop and operate the EFM and SGM
experiments, combining cryogenics, electronics, and scanning probe
microscopy. These complex experiments require good experimental skills
and a high motivation. The devices are prepared by collaborators in Paris
from high mobility GaAs/AlGaAs heterostructures.
Marc Sanquer (CEA, Grenoble) and Benoit Hackens (UCL, Belgium).
Ce stage pourra se poursuivre par une thèse : A PhD thesis is possible if a funding is obtained.
Formation / Compétences : Master in condensed matter physics and/or nanosciences.
(Matière quantique, Nanophysique, etc...)
Période envisagée pour le début du stage : February 2017
Contact : Hermann Sellier
Institut Néel CNRS-UGA, office: D418, tel: 04 76 88 10 86
[email protected]
http://www.neel.cnrs.fr/spip.php?article3282
47
Scanning gate microscopy on graphene quantum point contacts
Cadre général :
Graphene is a monolayer of carbon where unique electronic properties of massless Dirac fermions
result from a linear dispersion relation around the so-called Dirac points. At zero magnetic field, the
absence of energy gap makes the fabrication of nanostructures difficult using traditional metal gates.
In large magnetic fields however, the formation of Landau levels creates gaps in the spectrum, such
that the conducting edge channels follow the electrostatic potential of the gates. Recently, we
demonstrated the operation of quantum point contacts (QPC) in the integer and fractional quantum
Hall regime using a high mobility graphene encapsulated between boron-nitride flakes. These samples
are fabricated in the laboratory with a dedicated transfer setup allowing us to pick-up and release the
graphene and boron-nitride flakes one after each other to build a vertical stack. Two lithography steps
in clean room are then necessary to pattern the stack by etching and to deposit the electrodes.
During the internship, the student will learn this sample fabrication and then use a scanning probe
microscope at low temperature and under high magnetic field to investigate the physics of graphene
quantum point contacts in the quantum Hall regime. In particular, anomalous quantum Hall plateaus
have been observed that may originate from equilibration of the chemical potential between edge
states in the bulk and below the gates, an hypothesis that we would like to investigate further by
imaging the current paths by scanning gate microscope (SGM). This technique consists in tuning
locally the electrostatic potential inside the graphene with an AFM tip and by recording
simultaneously the effect on the device conductance, such as to build a map of the transmitted current
through the device. Perspectives for a PhD thesis could be an SGM study of quantum Hall
interferometers induced by the SGM tip itself close to a QPC.
Sujet exact :
The master student will fabricate his/her own
devices by exfoliation of graphite and boronnitride crystals, transfer of flakes to fabricate
heterostructures, and clean-room nanofabrication.
The student will also use our cryogenic AFM
microscope to carry out SGM experiments, first,
on existing QPC devices made out of
GaAs/AlGaAs heterostructures, and then, on
his/her own graphene devices. The student
should be interested both by sample fabrication
and by complex experiments.
This work will be supervised jointly by Hermann Sellier and Benjamin Sacépé (QNES team).
Ce stage pourra se poursuivre par une thèse : A PhD thesis is possible if a funding is obtained.
Formation / Compétences : Master in condensed matter physics and/or nanosciences.
(Matière quantique, Nanophysique, etc...)
Période envisagée pour le début du stage : February 2017
Contact : Hermann Sellier
Institut Néel CNRS-UGA, office: D418, tel: 04 76 88 10 86
[email protected]
http://www.neel.cnrs.fr/spip.php?article4205
48
Résolution de nouvelles structures cristallines par Movie-Tomography en
Diffraction Electronique
Cadre général :
En science des matériaux, il est primordial de bien connaître la structure cristalline d’un matériau pour
pouvoir comprendre ses propriétés physiques, et la diffraction électronique est un outil idéal pour
caractériser la structure de la matière. Cependant, certains matériaux s’amorphisent au bout d’une
quelques minutes sous faisceau électronique, ce qui requiert des techniques de caractérisation
structurales à la fois efficaces et rapides. Une technique adaptée en voie de développement est la
tomographie dans l’espace réciproque par enregistrement d’un film, ou « Movie-Tomography ».
En microscopie électronique en transmission, la diffraction électronique est l’un des nombreux modes
de travail pour étudier localement la matière, et les derniers développements autour de la
cristallographie aux électrons permettent de résoudre tout type de structure cristalline. Cependant,
l’enregistrement des données est relativement long (de l’ordre de l’heure et demi), et lorsque l’on a
affaire à des matériaux susceptibles de s’amorphiser sous le faisceau, il faut travailler avec des
techniques alternatives permettant l’enregistrement d’un jeu de données complet en un temps très
restreint. Pour cela, nous proposons la mise en
œuvre d’une méthode appelée « MovieTomography », qui consiste à se positionner sur
une zone du matériau à étudier, puis tilter en
continu le porte-échantillon sur toute sa gamme
de tilt, tout en enregistrant un film dans l’espace
réciproque. Ensuite les différents clichés de
diffraction électronique constituant le film sont
extraits, puis exploités par les différents logiciels
de cristallographie permettant l’extraction des
intensités des réflexions de Bragg et ainsi la
résolution de la structure. Le stage consiste donc
à résoudre les structures de nouveaux matériaux
pour l’énergie par Movie-Tomography. Nous étudierons l’influence des différents paramètres
d’acquisition sur la précision des données. En guise d’exemple, la figure ci-dessus présente les
premiers résultats de cette technique appliquée sur le composé Na2VO(PO4)2 : A gauche : 2 coupes du
réseau réciproque avec les réflexions de Bragg indexées, conduisant à la détermination de la maille et
du groupe d’espace. A droite : premier résultat de modèle structural obtenu sur le composé
Na2VO(PO4)2 par movie-tomography.
Interactions et collaborations éventuelles : Avec la chimiste qui synthétise les matériaux et les
microscopistes de l’Institut Néel.
Ce stage pourra se poursuivre par une thèse (ou ce sujet est limité à un stage M2...) : Oui, par
une demande de financement auprès d’une école doctorale.
Formation / Compétences : Il faut un bon niveau en cristallographie et en chimie du solide.
Période envisagée pour le début du stage : Janvier à juin 2017
Contact : Lepoittevin Christophe
Institut Néel - CNRS : tél : 04 76 88 71 92. mail : [email protected]
49
Quantum Hall interferometry in high mobility Graphene
Graphene is a 2D material that has attracted a huge interest since its discovery in 2005. Its gapless linear band structure that mimics massless Dirac fermions has led to the discovery of a wealth of new exciting transport properties. Moreover, the possibility to engineer very high mobility graphene devices in which electrons can travel in a ballistic fashion makes graphene the perfect playground to investigate new quantum coherent phenomena and interaction effects in the integer and fractional quantum Hall regimes. The goal of the internship is to study an electronic analogue of the optical Fabry-‐Pérot interferometer in the quantum Hall regime of graphene. In the quantum Hall effect, electron transport is confined in one-‐dimensional channels that propagate along the edges of the sample. The use of electrostatic gate electrodes enables the control of their path to modify the interference pattern, and also the realization of constrictions (quantum point contacts [1]) that act as semi-‐
reflecting mirrors for electron wave packets. These two basics elements are the keys to engineer quantum Hall interferometers (see figures). During the internship, the student will learn the van-‐der Waals pick-‐up technique used to make high mobility graphene devices and carry out measurements on state-‐of-‐the-‐art devices to unveil quantum interferences. To enter the quantum Hall regime and study the physics of quantum Hall interferometers, low-‐noise quantum transport measurements will be performed at very low temperature (~10mK, dilution fridge) and high magnetic field (18T). The student will be involved at all levels, from the device fabrication process, to the transport measurements at very low temperature and high magnetic field, to the data analysis and interpretation. For the PhD perspective, efforts will be focused on two important objectives, namely investigating the nature of the fractional quantum Hall effect with interferometers, and the interplay between the quantum Hall effect and superconductivity. [1] K. Zimmermann et al, Gate-‐tunable transmission of quantum Hall edge channels in graphene quantum point contacts. http://arxiv.org/abs/1605.08673 Ce stage pourra se poursuivre par une thèse : Yes (PhD grant funded by a european ERC project) Formation / Compétences : We look for highly motivated students with a strong background in condensed matter physics / quantum physics, and which are willing to address fundamental questions of advanced quantum solid-‐states physics. Période envisagée pour le début du stage : early 2017 Contact : Benjamin Sacépé Institut Néel – CNRS Quantum Nano-‐Electronics and Spectroscopy (QNES) team (http://neel.cnrs.fr/spip.php?article4205) [email protected] Tel: 04 76 88 10 79 50
Visualizing quantum Hall edge channels in Graphene
Quantum Hall effect in two-‐dimensional electron gases has been thoroughly studied for the last decades. Its transport properties rely on the existence of one-‐dimensional conducting channels that propagates along the edge of the sample, each carrying a quantum of conductance (𝑒 ! ℎ). Despite the large amount of work available on the topic, very little is known about the exact nature and spatial structure of these edge channels. Our group is leading a European research program that aims at performing the first real-‐space visualization of quantum Hall edge channels in graphene by means of scanning tunneling microscopy (STM) and spectroscopy. The goal of the internship is to perform preliminary STM spectroscopy of the Landau levels a
b
c
Figure | a. Schematic drawing of the STM measurement principle of quantum Hall edge channels. b. The STM spectroscopy gives direct access to the local electronic density-‐of-‐states (DOS) with atomic resolution. The Landau levels will appear as peaks in the DOS. c. 3D sketch of the STM head. in graphene under high magnetic field. The student will learn state-‐of-‐the-‐art STM instrumentation, and participate in the fabrication of dedicated graphene devices that are suitable for STM measurement. To obtain well resolved Landau levels, high mobility devices will be made by micro-‐transfer of graphene on a hexagonal boron-‐nitride substrate. Measurements will be performed with a newly developed STM head which is cooled down at very low temperature (10mK, dilution fridge) and subjected to a high magnetic field (14T). The STM microscope is capable to work in atomic force microscope (AFM) mode, enabling for large scan area on insulating substrates in order to locate graphene devices. The student will be involved at all levels, from the device fabrication process, to the STM measurements at low temperature and high magnetic field, to the data analysis and interpretation. This study is the first step towards a pioneer investigation of quantum Hall edge channels. The ensuing PhD work will focus on the detailed study of the considerable spatial structure of quantum Hall edge channels, both in the integer and in the fractional quantum Hall regimes. Ce stage pourra se poursuivre par une thèse : Yes (PhD grant funded by a European ERC project) Formation / Compétences : We look for highly motivated students with a strong background in condensed matter physics / quantum physics, and which are willing to work with remarkable instrumentation and address fundamental questions of advanced quantum solid-‐states physics. Période envisagée pour le début du stage : early 2017 Contact : Benjamin Sacépé Institut Néel – CNRS Quantum Nano-‐Electronics and Spectroscopy (QNES) team (http://neel.cnrs.fr/spip.php?article4205) [email protected] Tel: 04 76 88 10 79 51
Bio-Activation of Mesoporous Silica Nanoparticles by selective DNA
destructuration
Summary :
This project aims at synthesizing mesoporous silica nanoparticles (MSNs) containing hosts in the
pores and gated using DNA fragments. The cleavage of the DNA fragments by enzymes will allow the
opening of the pores, thus the release in solution of the cargo. This will be applied for the detection of
DNA-repairing enzymes.
Detailed subject:
Mesoporous silica nanoparticles (MSNs) constitute a family of nanoparticles (ca 100 nm in diameter)
that is widely used for drug delivery owing to the rigidity of the matrix, the high porosity and the
possible chemical modification of the surface. Interestingly, the pores (ca 2-3 nm in diameter) can be
blocked when nanovalves are grafted, which destroy when a specific stimulus is applied. This has
been exemplified with DNA fragments [1].
In this project, we wish to use the same principle for sensing DNA-repairing enzymes [2]. MSNs will
be gated with DNA fragments containing lesions. When the repairing enzyme specific to the lesion is
present, the pore-gating DNA will be cleaved and the contents of the pores will be expelled, leading to
a measurable signal.
This project gathers the expertise of Didier Gasparutto (CEA/INAC/SyMMES) in the synthesis of
DNA architectures, and of Xavier Cattoën (Inst Néel) in the synthesis and functionalization of
mesoporous silica nanoparticles. [3]
[1] Schlossbauer, et al, Angew. Chem. Int. Ed. 2010, 49, 4734
[2] G. Gines, C. Saint-Pierre, D. Gasparutto ; Biosensors & Bioelectronics (2014) 58, 81-84
[3] A. Noureddine, X. Cattoën, M. Wong Chi Man, Nanoscale 2015, 7, 11444–11452
Collaboration:
Strong collaboration with Didier Gasparutto (CEA/INAC/SyMMES).
This internship may be followed by a PhD thesis.
The student should have expertise in chemical synthesis and materials characterization, and a basic
knowledge in biochemistry.
Période envisagée pour le début du stage : 02/2017
Contact : Cattoën Xavier
Institut Néel - CNRS : 04-76-88-10-42 [email protected]
52
Confined nucleation and growth of molecular nanocrystals for biophotonics
and advanced solid-state NMR
General Scope: The shaping of molecular nanocrystals (NCs) in solutions allow to enhance the
sensitivity (by several orders of magnitude) and the resolution of a just emerging magnetic resonance
spectroscopy called Magic Angle Spinning - Dynamic Nuclear Polarization (MAS-DNP), developed at
CEA-INAC. This MAS-DNP spectroscopy will be used to 3D structure determinations (NMR
crystallography) of many solid-state systems, which do not easily form large enough crystals (>100
mm) suitable for single crystal X-ray diffraction studies and cannot be easily isotopically enriched in
13
C and 15N. Thus, such developments are highly relevant, especially for supramolecular systems,
drugs, natural products, self-assembled peptides/nucleotides… etc. On the other hand, we have
managed so far the confined nucleation of molecular NCs in sol-gel matrices for biophotonics. Indeed,
organic NCs can exhibit intense fluorescence emissions and good photo-stability, which are promising
for biological tracers (medical imaging based on fluorescence contrasts). In this case, the NC surface
is covered by a silicate shell, which can be functionalized to obtain biocompatible and furtive coreshell nanoparticles in vivo.
Research topic and facilities available: The objective will be to control the confined nucleation and
growth of molecular NCs in droplets of organic solvents. For that, organic compounds will be
dissolved in solvents miscible with water (alcohols, THF, dioxane …). The resulting solutions will
be sprayed and suddenly dispersed in water. As water is generally a non-solvent for molecular
phases, the corresponding NCs will grow when the solvent droplets will be gradually mixed in water.
We recently made a step-forward in the control of this process by producing nanometer-sized
crystals of progesterone (around 50 nm in diameter) as shown by scanning electron microscopy in
the figure below. The goal is now to produce monodisperse initial droplets to obtain then narrow size
distributions of NCs (50-100 nm) by optimizing the nanocrystallization reactor and confined
nucleation conditions. The resulting NCs will be characterized by X-ray diffraction, electron
microscopies (SEM and TEM), dynamic light scattering, Raman and fluorescence spectroscopies.
This research is part of a highly challenging ERC (European Research Council) project on
developments of MAS-DNP spectroscopy. Indeed, we believe that our generic process will be
widely applicable for molecules exhibiting both a large solubility in solvents miscible with water and
a negligible solubility in water, which is the case of a large number of organic compounds. Finally,
we will plan to couple this confined nanocrystallization method in solutions to sol-gel chemistry, in
order to prepare through a one-step process core-shell nanoparticles: fluorescent NCs surrounded by
an amorphous silicate crust for medical imaging applications.
Nanocrystals of progesterone obtained from a methanol solution, sprayed and injected in water.
Possible collaborations and networking: INAC-CEA, CERMAV-Grenoble, CHU-Grenoble …
Required skills: Solid-state and physical chemistry, basic knowledge on physicochemical and
structural characterizations of materials.
Starting date: 2017
Contact : Alain Ibanez, Institut Néel, CNRS. Phone: 0476887805 e-mail: [email protected]
53
E-beam electromechanics for quantum nanomechanical engineering
General Context:
Micro-electromechanical systems have dramatically developed over the past 40 years to become
indispensable in modern technology. This success prominently relies on the reduced dimensions of
these devices, enabling both high level of integration and ultra-high sensitivity in a variety of
applications such as navigation, communication and connected objects.
The recent progress in nanotechnology have raised the perspective to further push this approach to
nanomechanical systems, with a corresponding size reduction of more than 3 orders of magnitude.
However this challenge has so far
remained unsuccessful: While being
their main strength, the extremely
reduced
dimensions
of
nanomechanical
systems
also
represent their Achilles’ heel, making
them both extremely difficult to detect
and overly sensitive towards external
Fig. (a) SEM micrograph of InAs nanomechanical wires. (b) Brownian
perturbations.
motion spectrum of an InAs nanomechanical wire as obtain using the e-beam
The hosts of the proposed project have
nano-elecromechanical measurement technique.
recently started developing a novel
generation of all-integrated hybrid optomechanical components which appear as very promising
candidates for tackling the above stated obstacles1. The principle of these devices relies on suspended
semiconducting photonic nanowires2 incorporating their own motion readout system, consisting in a
quantum dot implanted near their basis. The main ambition is to scale down this concept to nanowires
with dimensions in the 10 nm range. Because of its disruptive nature, this research requires to
reconsider the whole scientific and technological methodology in order to validate and optimize the
proposed approach. In particular, efficient nanomechanical motion readout methods at these scales
have been so far missing.
Project:
The present project proposes to investigate a newly introduced readout scheme enabling ultra-sensitive
nanomechanical detection of objects with dimensions down to the nanometer level. The method relies
on detecting the fluctuations of the scattered electrons current inside a scanning electron microscope3.
The hosts of the project have started to successfully implement this approach for detecting the thermal
motion of semiconducting InAs nanowires (cf. Fig. (a)) with a very high sensitivity (see Fig. (b)).
This M2 internship will investigate this electromechanical interaction over various semiconducting
and conducting materials (GaAs, Si, Carbon nanotubes…) both at ambient and cryogenic temperatures,
with the perspective to characterize and stabilize the measurement backaction effects. Possibilities to
couple this scheme to cathodoluminescence measurement can be envisioned in a PhD work.
References
1
I. Yeo, et al, Nature Nanotechnology 9, 106 (2014)
J. Claudon et al. Nature Photonics 4 (3) 174-177 (2010)
3
A. Niguès et al. Nature communications 6, 9104 (2015)
2
Possible collaboration and networking : J. Claudon, J.M. Gérard, M. Hocevar (CEA/INAC),
S. Pairis and F. Donatini (Institut Néel), P. Verlot (ILM, Lyon), A. Bachtold (ICFO, Barcelone)
This internship can go on to a PhD
Required profile : This experimental internship deals with nanomechanics, quantum optics, semiconductor physics, and electronics
Expected start for the internship : First half of 2017
Contact : Jean-Philippe POIZAT, Tél : 04 56 38 71 65 mail : [email protected]
More on : http://neel.cnrs.fr/spip.php?rubrique47
54
Electroless deposition of magnetic nanotubes and core-shell nanowires for a
3D spintronics
General Scope:
There are proposals to develop a spintronic technology in three dimensions, to lift foreseen limitations
of areal density faced by any 2D-based technology such as hard disk drives. Chemical synthesis is the
best route to deliver 3D systems such as dense arrays of wires, and joint work between chemists and
the spintronic community are emerging. These systems also offer opportunities for new fundamental
science of domain walls and spin waves, due to the confined geometry, different topology (circular
boundary conditions), and curvature-specific physics [1].
In this context we are pioneering the study of magnetic
nanotubes, yet another novel geometry. These are obtained
flux-closure
by magnetic
electroless
plating,domains
also widely used in industry for
deposition of coatings on various surfaces, including nonconducting and of high-aspect ratio. It relies on reduction of metallic ions from dissolved salts
by a reducing chemical agent. By performing the deposition in nanoporous
templates one can deposit large arrays of magnetic nanotubes with
diameters down to 100 nm [2]. Various material can be deposited ranging
from simple metals to more complex compounds [3] – e.g. NiCoB (see Fig.,
our own work) [4].
[1] Streubel et al., J. Phys. D: Appl. Phys. 49 , 363001 (2016). [2] Li et al., CrystEngComm
16, 4406 (2014).
[3] Richardson et al., ECS Trans. 64 (31), 39-48 (2015). [4] Schaefer et al.,
RSC Adv., 6, 70033 (2016)
Fig.: NiCoB tube, from the left: structure+XMCD-PEEM, Transmission electron
microscopytopic and facilities available:
Research
The project consists in opening routes to fabricate multi-layered nanotubes, or in other words, coreshell. The motivation is to apply the standard concepts required to implement nanomagnetism and
spintronics in a planar technology, to a 3D geometry (eg: ferro/metal/ferro for giant magnetoresistance). This will be done by combining successive electroless plating steps, and/or with Atomic
Layer Deposition and/or direct electroplating. This will be done on existing facilities. Structural
characterization will be performed using atomic force microscopy, scanning and possibly also
transmission electron microscopy, chemical analysis by Energy Dispersive X-ray spectroscopy.
Magnetic properties will be evaluated on both arrays of tubes (magnetometry, tubes still in the
template) and on isolated tubes dispersed on a flat substrate by focused Kerr (magnetooptics) or
magnetic force microscopy. Support of micromagnetic simulation is provided.
The project is led as a collaboration between INAC/Spintec (O. Fruchart) and Institut Néel. It is part of
a larger effort involving international collaboration (TU Darmstadt, FAU Erlangen, Synchrotrons).
Possible extension as a PhD: Yes, preferable.
Required skills:
Physics/Chemistry at bachelor level. A taste for experimental and multidisciplinary work is
appreciated. Welcome: physical chemistry, nanomagnetism, characterization techniques
Starting date: 1st March 2017 (flexible)
Contact:
Name: M. Stano / L. Cagnon (Institut Néel – CNRS). O. Fruchart (SPINTEC)
E-mails: [email protected] / [email protected] / [email protected]
55
Quantum superpositions of causal relations
General context:
The study of causal relations has recently gained a lot of interest in the fields of quantum foundations
and quantum information. The general objective is to investigate the possible causal relations between
events that can exist in the quantum world, and see how they differ from classical relations.
For instance, just like quantum objects can be in a superposition of two incompatible states, one may
wonder if there can be superpositions of causal relations: e.g., for the case of 2 events A and B, a
situation of the kind “|A causes B> + |B causes A>”.
A framework was recently developed [1] to analyse
quantum processes that are incompatible with a
definite causal order (i.e., for which one cannot
say that A acts before and causes what happens at B,
or vice versa). Such processes are called causally
The quantum switch: the 2 polarizing beam splitters
non-separable; an example is the quantum
(PBS) transmit horizontally polarised photons and reflect
vertically polarised ones; a |H> photon will thus go to A
switch [2] represented on the right. The framework
and then to B, while a |V> photon will go to B and then to
also allows for processes that generate some new
A. A photon in a quantum superposition |H>+|V> will
kind of noncausal correlations, which violate sothus go to A then B, and B then A, in superposition.
called causal inequalities; it remains however an
open question, whether such processes can indeed be realised in practice.
Research project:
This project aims at investigating various new practical examples of quantum processes, to test their
causal nonseparability and their possible ability to violate causal inequalities. The candidate will resort
in particular to the useful analogy between causal nonseparability and entanglement, and between
causal inequalities and Bell inequalities [3]. Some of the examples under investigation may not be
described in the current form of the framework of [1], which will lead the candidate to propose
possible ways to generalize the framework. Various types of “superpositions of causal relations” will
be considered, which may involve more than 2 events.
[1] O. Oreshkov, F. Costa, and Č. Brukner, Nat. Commun. 3, 1092 (2012).
[2] G. Chiribella et al., Phys. Rev. A 88, 022318 (2013); M. Araújo et al., Phys. Rev. Lett. 113, 250402 (2014).
[3] M. Araújo et al., New J. Phys. 17, 102001 (2015); C. Branciard et al., New J. Phys. 18, 013008 (2016).
Interactions and possible collaborations:
This project will be supervised by Cyril Branciard, and will be conducted in collaboration with the
theory group of Alexia Auffèves. The candidate will benefit from interactions with the other group
members and from their expertise in a large range of domains (quantum foundations, quantum
information, quantum optics, cavity and circuit QED, quantum thermodynamics…). Interactions will
also be possible with the group of Prof. Nicolas Gisin at the University of Geneva (Switzerland).
This project may be followed by a PhD depending on funding opportunities.
Training / Skills:
A good knowledge of the formalism of quantum theory and a strong interest in fundamental physics,
in particular in quantum foundations and quantum information, are required.
Starting date: early 2017
Contact: Branciard Cyril
Institut Néel – CNRS. tel: 04 56 38 71 64; e-mail: [email protected]
More information on: http://neel.cnrs.fr
56
New generation of phosphors for eco-efficient LED lighting: Pechini
method
General Scope: Lighting by "white LEDs" has become a major challenge for energy saving. However,
several problems need to be overcome, the most important are: cost, quality of the white
photoluminescence emission and thermal stability. Currently, all devices used, or in development,
involve rare earth ions whose main drawbacks are lighting with narrow emission bands with a
significant blue component and also their high cost as they are highly strategic elements due to the
monopoly of their production by China. At the Institut Néel, we develop a new type of phosphors
based on vitreous powders to achieve white LEDs for solid lighting. The innovative character of these
aluminum borate phosphors is to produce a broadband luminescence emission throughout the visible
spectrum, from color centers (structural defects) in an amorphous matrix. In addition, these phosphors
are made of non-toxic and abundant, no rare earth thus making them much less expensive. The project
is the pursuit of original work (thesis and patent), which has been initiated in recent years. These
phosphors are synthetized by two different “chimie douce” routes: - modified pechini method
(polymeric precursors) - sol-gel method (alkoxide precursors); each method leading to a master topic.
Research topic and facilities available: the aims of this stage are, firstly: - Understanding the origin
of the emitting centers, which are related to structural defects (carbon interstitials...) in order to
optimize the luminescence properties. The optimization of the synthesis of these phosphors will be
performed by the modified Pechini route, varying chemical factors (nature and stoichiometric ratios
of molecular precursors which allow the metal complexation and the polymerization of organicinorganic network) - change the chemical composition, which is expected to adjust the width of the
spectral luminiscent emission in order to improve the light color rendering. A study of the different
parameters of thermal treatments (heating rates, the ranges of temperature, controlled atmosphere
during treatment), which are at the origin of the presence of emitting centers. Finally, the
understanding of the origin and role of emitting centers and the structural characterizations and
modeling of the amorphous phase will be implemented by coupled spectroscopic studies: FTIR,
UV-Vis spectroscopy, EPR, NMR, X-ray diffraction and X-ray scattering.
Left) Schematic of the process steps: from liquid resin to a luminescent powder. Right) emission spectrum of
powder showing a residual peak of the UV incident radiation, non-absorbed by the phosphor, and the broad
PL emission band of the phosphor in the whole visible range, between 400 and 800 nm leading to good color
coordinates.
Possible collaboration and networking: LMGP-Grenoble ; Institut de Recherche Chimie-Paris ;
INAC-CEA Grenoble
Required skills: Solution chemistry, basic knowledge on physicochemical and structural
characterizations of material
Starting date: Feb. 2017
Contact
Name: Salaün Mathieu
Phone: 04 76 88 10 42 e-mail: [email protected]
More information : http://neel.cnrs.fr
57
Mesure de fluctuations de vitesse par anémométrie à fibre optique
Cadre général :
La physique de la turbulence est étudiée depuis plus d’un siècle mais elle demeure un sujet ouvert. Au
sein d’un écoulement turbulent, des tourbillons de tailles différentes interagissent. L’étude de ces
interactions entre structures et la compréhension des caractéristiques des très petites échelles constitue
un défi majeur qui nécessite la miniaturisation des sondes de mesure. Les capteurs doivent être
suffisamment petits pour résoudre les plus petites structures tout en étant robustes et sensibles.
Dans cet esprit, nous avons entrepris à l’Institut Néel le développement d’un anémomètre à fibre
optique. Les premiers essais ont montré que le principe de fonctionnement de la sonde est valide (voir
Figure). Un nouveau prototype est en cours de réalisation. Afin de permettre l’exploitation de la sonde,
il est maintenant important de caractériser sa réponse dans un écoulement.
Fig. [à gauche] L’écoulement arrive par la gauche et défléchit la membrane. Son déplacement est
mesuré par la fibre optique (d’après Watson et al.) [à droite] Capteur commercial à fibre (FISO).
Nous souhaitons recruter un étudiant en stage afin d’adapter les moyens de tests de l’Institut à l’étude
du comportement de la sonde. Pour cela, un écoulement d’air comprimé filtré sera utilisé pour
produire un signal de turbulence connu. La sonde sera montée sur une tête goniométrique. L’étudiant
devra monter le banc de test à partir de ces différents éléments et l’instrumenter. Il effectuera ensuite
une étude systématique de la réponse dynamique de la sonde en fonction de l’angle d’incidence. Le
traitement des données devra permettre de caractériser les performances de la sonde. De ce travail
dépendra la nouvelle génération de ce type de capteur.
L’anémomètre est développé au sein d’une collaboration interne à l’Institut Néel, entre des
hydrodynamiciens et des opticiens. L’étudiant sera amené a interagir pleinement avec les différents
acteurs de la collaboration. Il devra également collaborer avec les équipes techniques du laboratoire
pour les questions de mécanique.
Formation / Compétences : Compétences développées: Optique fibrée, Instrumentation,
Hydrodynamique & Turbulence, Acquisition & Traitement du signal.
Contact : Chabaud Benoit, Institut Néel – CNRS/UGA, [email protected]
(contacts alternatifs : Philippe Roche, [email protected] , et Jochen Fick, [email protected] )
Site web : http://hydro.cnrs.me
58
Growth conditions to stabilize polar faces of ferroelectric crystals
General Scope:
Periodically poling of KTiOPO4 (KTP) crystals by electric field poling is the way to improve the
conversion efficiency by the quasi-phase matching technique [H. Karlsson and F. Laurell, Applied
Physics Letters 71, 3474 (1997)].
Electric field poling technique leads
to periodically poled crystals of
limited thickness that is detrimental
to obtain high power application. A
way to getting around this limitation
consist in the growth, from high
temperature solutions, onto polar
faces of periodically poled KTiOPO4
(PPKTP) thin slabs obtained by
electric field poling [A. Peña, et al.,
Optical Materials Express 1, 185
(2011) and Journal of Crystal
Growth 360, 52 (2012)].
Nevertheless, this growth process have to take into account kinetic and thermodynamic considerations
in order to propagate the grating periodicity of the initial seed to the as grown layer.
The research project will be focused in doing several growth experiments onto single domain KTP
slabs in order to determine the stability of {001} polar faces. The first objective of the project is to
find the experimental conditions to be able to stabilize both non-equivalent polar faces, (001) and (001). The second one is growing these faces at the same growth rate to be able to grow thick PPKTP
crystals to be used in high power optical devices.
The growth devices are available in the technical services (pôle Cristaux Massifs of MCBT
department) and the SEM and AFM in the technical services (pôle Optique et microscopies of PLUM
department) of Institut Néel.
The master 2 stage is going to be under the supervison of Alexandra Peña Revellez(CR1, OPTIMA
research team) and in close interaction with Bertrand Ménaert (IRHC, pôle Cristaux Massifs), and
Benoît Boulanger (PRCE1, OPTIMA research team). Collaborations, Jérôme Debray (IE2, pôle
Cristaux Massif) will also be important.
The internship could move on a PhD if financial support is found.
Required skills:
Materials science
Skills in crystal growth will be appreciate
Starting date:
March 2017
Contact:
Name: Alexandra Peña Revellez
Phone: (33) 4 76 88 79 41
(33) 4 76 88 78 03
[email protected]
59
Growth of the chiral ferromagnet LiFe5O8 by high temperature flux
method
General Scope:
Chiral magnetic compounds, forming chiral structures both crystallographically and magnetically, has
been the subject of considerable interest lately due to unique magnetic properties such as magnetochiral dichroism (MChD) and nonreciprocal magnon propagation [Y. Iguchi, et al., Phys. Rev. B 92,
184419 (2015)]. Such phenomena can be cancelled by racemic twin crystals, so it is important to find
the experimental conditions to grow
homo-chiral single crystals.
The chiral ferromagnet LiFe5O8 is
attractive because it shows a high
magnetic transition temperature at
655 °C [E. Rezlescu, et al., Cryst. Res.
Technol. 31, 739 (1996)]. It undergoes a
structural phase transition at around
720 °C from a high temperature centrosymmetric structure (Fd-3m space
group) to a chiral one (P4132 or P4332
space group).
The growth of homochiral crystals LiFe5O8 is a big challenge. Indeed, the fluxes tried so far does not
allow to grow the crystal below their phase transition temperature of 720°C. Recently, during a
collaboration between Hiroshima University and Institut Néel, a promising new flux system that will
allow growing this crystal below its phase transition temperature has been identified. The main
objective during the internship is the growth of LiFe5O8 crystals in the new flux and determine
whether they are homochiral or not.
The growth devices are available in the technical services (pôle Cristaux Massifs of MCBT
department) and the X-ray facilities in the technical services (pôle X’Press of PLUM department) of
Institut Néel.
The master 2 stage is going to be under the supervison of Alexandra Peña Revellez(CR1, OPTIMA
research team) and in close interaction with Bertrand Ménaert (IRHC, pôle Cristaux Massifs) and
Isabelle Gautier-Luneau (PR1, OPTIMA research team). Collaborations, Olivier Leynaud (IR2, pôle
X’Press) will also be important.
The internship could move on a PhD if financial support is found.
Required skills:
Materials science
Skills in crystal growth will be appreciate
Starting date:
March 2017
Contact:
Name: Alexandra Peña Revellez
Phone: (33) 4 76 88 79 41
(33) 4 76 88 78 03
[email protected]
60
Turbulence Quantique : étude expérimentale
Cadre général :
T
En dessous de 2,17 K, l’hélium liquide acquiert des
propriétés superfluides : il peut s’écouler sans viscosité et la
vorticité de son champ de vitesse devient quantifiée. On s’attend
donc à ce que sa turbulence, appelée « Turbulence Quantique »,
diffère de la turbulence « classique ».
D’après plusieurs études récentes, il semble que la principale
différence soit concentrée au niveau des plus petits tourbillons
présents dans ces 2 types de turbulence. En effet, en l’absence
d’une dissipation efficace, on s’attend à ce que les tourbillons
superfluides s’accumulent aux petites échelles de
l’écoulement.
Tube de Pitot miniaturisé
permettant la mesure de
fluctuations de vitesse superfluide
L’objectif est de détecter et comprendre cette différence, grâce à un détecteur conçu à cet effet.
Dans le cadre du stage et de la thèse, l’étudiant développera un capteur de vortex miniature (<100 µm)
en tirant profit de l’environnement grenoblois en nano-technologies (nanofab, PTA/Minatec). Ce
capteur sera ensuite exploité dans nos différents écoulements d’hélium liquide, soit superfluide soit
classique, afin de comparer les propriétés physiques des deux types de turbulence. L’un de ces
écoulements sera la soufflerie TOUPIE, spécialement construite pour répondre à cet objectif, et qui
bien vient de bénéficier d’un upgrade pour atteindre des températures approchant 1K, un record pour
une soufflerie cryogénique de grande taille.
Le projet s’inscrit dans le cadre du projet inter-laboratoires
(CEA/CNRS/ENSL/INP/UGA) SHREK (financement ANR), centré sur
une cellule d’étude de la turbulence superfluide de très grande taille
(env. 1m3). Des expériences seront aussi conçues pour cette cellule.
Tourbillons superfluides
(simulation)
Formation / Compétences développés : Hydrodynamique & Turbulence quantique, Physique des
basses températures & Cryogénie, Nanotechnologie & Technique de microfabrication, Acquisition &
Traitement du signal, Instrumentation & Mesures bas bruit
[email protected] (04 76 88 11 52) http://hydro.cnrs.me
61
Dielectric properties of the Cooper-pair insulator
When a superconducting disordered thin film is subjected
to an increase of disorder or to a strong magnetic field (B)
it can undergo a transition to an insulating state. This
transition is a quantum phase transition (driven by a
change of a parameter of the Hamiltonian at T=0) between
two antinomic ground states, the superconducting and
insulating ground states. In recent years the insulator drew
significant interest due to the body of experimental work
that indicates that charge carriers in it are localized
Cooper-pairs [1]. It is thus considered as a unique
playground to investigate an interacting, many-body
quantum system of localized Cooper-pairs in a disordered
potential.
The transition to the so-called Cooper-pair insulator is
easily tuned in experiments by applying a strong
perpendicular magnetic field. The above figure shows a typical B-tuned transition from
superconductor at B=0 to the Cooper-pair insulator at finite B with a diverging magnetoresistance
resistance peak at the lowest temperature. The nature of the insulator in this magnetoresistance peak is
the focus of our current research activities.
The goal of this Master project is to perform innovative high frequency measurements of the dielectric
properties of the Cooper-pair insulator using state-of-the-art superconducting micro-wave resonators.
The underlying physics to unveil is a possible signature of a new transition to a new insulating state
with strictly zero conductivity at finite temperature (called many-body localized state) [2]. The student
will participate in the design of RF superconducting resonators that serve to probe of the dielectric
constant. She/He will prepare and characterize superconducting samples by magneto-transport
measurements (down to 10mK and 18T), and start the first high frequency measurements of the
dielectric constant. These initial measurements will give crucial information about the role of
Coulomb interaction in the superconductor insulator transition.
[1] B. Sacépé et al. Localization of preformed Cooper pairs in disordered superconductors, Nature
Physics 7, 132 (2011). http://arxiv.org/abs/1012.3630
[2] M. Ovadia et al. Evidence for a Finite Temperature Insulator. Nature Scientific Reports 5:13503
(2015) http://www.nature.com/articles/srep13503
Interactions et collaborations éventuelles : Superconducting resonators : Alessandro Monfardini,
HELFA team. Landau Institute for Theoretical Physics (Moscow). Weizmann Institute of Science.
Formation / Compétences : We look for highly motivated students with a strong background in
condensed matter physics / quantum physics, and which are willing address fundamental questions of
advanced solid-states physics.
Période envisagée pour le début du stage : early 2017
Contact : Benjamin Sacépé, Institut Néel – CNRS
Quantum Nano-Electronics and Spectroscopy (QNES) team (http://neel.cnrs.fr/spip.php?rubrique49)
[email protected] Tel: 04 76 88 10 79
62
Synthesis of Chiral Crystals for magnetism, spintronic and Nonlinear
Optics
Cadre général :
This subject aims at synthesising and then studying the growth of two chiral compounds in order to
obtain large, homochiral crystals. The two selected compounds are quite similar : CsCuCl3 and
CsGeCl3. The first one is a chiral magnet with exotic properties of great interest for science
(nonreciprocal magnon propagation,…) and applications (spintronic) that are studied by Japanese
collaborators (Pr. K. Inoue and Y. Kousaka, Hiroshima University). The second commpound has
recently been shown as a potential non linear optical frequency converter in the visible to the far infrared (0.3-20µm) which is the main interest of part of our group at Institut Néel. Yet no single crystal
have been grown and no real non linear study have been performed on this compound. This work will
thus involve first the synthesis of the compounds and then the study of theire crystal growth in a
dedicated growth reactor. Once crystals of a few mm are obtained, conditions favoring an
enantiomorphic selective crystallization will be studied by adapting condition employed in Viedma
ripening.
In order to grow large homo-chiral CsCuCl3
single crystals we propose to use our rapid
growth system developed and patented by
Institut Néel It proved remarkably efficient at
growing large (5-7cm) single crystals of high
purity and high quality of KH2PO4 and the
K(D1-xHx)2PO4 solid solution used as case
studies (Figure 1). The first exploratory growth
runs of CsCuCl3 with this system proved very
encouraging. The determination of the optimal
growth conditions (solvent, temperature, Figure 1 Large (5 cm) KH PO high purity and high
2
4
growth rates, …) should now be undertaken in quality single crystal grown at about 10 mm/day by the
order to provide to the physical studies the method patented by Institut Néel
large homo-chiral single crystals they require.
In the case of CsGeCl3, two synthesis routes exist in the literature; both are done at moderate
temperatures (<100°C) and employ standard chemicals. Yet the exact conditions leading to the highest
synthesis yields of CsGeCl3 should be explored. The similarity with the previous compound will allow
to transpose almost directly all the growth conditions to this new compound.
Finally, ways to influence the chirality of the crystals synthesized have recently been identified (called
Viedma ripening) by using grinding or thermal cycling, our growth method being compatible with
both, their introduction in the process will be tested to determine their impact on the homochirality of
the grown crystals.
Possible collaboration and networking :
Possible extension as a PhD : No
Required skills : Solution chemistry, knowledge in physicochemical and structural characterizations
of materials
Contact : ZACCARO Julien
Institut Néel - CNRS : phone : 04 76 88 7804 email : [email protected]
More info sur : http://neel.cnrs.fr
63
Quantum simulation in circuit-QED
Scientific Context: While the universal quantum computer is a very promising but very demanding
route towards quantum computation, quantum simulators appear as a faster approach to quantum
speedup. Based on an idea initially suggested by R. Feynman, a quantum simulator is a machine
dedicated to a given class of physical problems (e.g. quantum magnetism, fermionic or bosonic
Hubbard models...). The required building blocks (quantum bits) as well as the control electronics are
similar to the one of the universal quantum computer but since universality is not required, the
overhead developments are less stringent. As such, they are considered as the first architecture, which
will allow tackling problems intractable with classical computers.
We are developing a
quantum simulators based on
superconducting
quantum
bits coupled to microwave
photons. This architecture has
100 µm
been dubbed circuit Quantum
ElectroDynamics
(circuitb
c
QED), for a recent review
you can look at [1]. The
quantum
simulator
we
1 µm
300 nm
demonstrated recently (see
figure) aims at unraveling
a. Overview of the first generation of our quantum simulator
quantum impurity problems,
(Optical microscope image). It is made of a superconducting
which are integral to the
quantum bit (red rectangle) coupled to superconducting metaunderstanding of strongly
materials (blue rectangle). b. Detail of the meta-material, which is
correlated materials or highmade of 5000 Josephson junctions (SEM image). c. Josephson
Tc superconductors [2].
junction forming the quantum bit (SEM image).
[1] Devoret, M. H., & Schoelkopf, R. J. Science, 339(6124), 1169–1174 (2013).
[2] Snyman, I., & Florens, S. Physical Review B, 92(8), 085131 (2015).
Description, available means: Our team has a strong experience in nanofabrication, microwave
electronics and cryogenic equipment. The student will first design and fabricate a new generation of
our quantum simulator in the clean room of the Neel Institute (Nanofab). She/He will then carry out
the measurements of the device at very low temperature (20mK), using one of the three fully equipped
dilution refrigerators of the team. The “Agence Nationale pour la Recherche” (National French
Funding Agency) recently funded this project.
Interactions and collaborations: Our team is part of several national and international networks. For
this specific project we are collaborating closely with the group of Serge Florens at the Néel Institute
and with the group of Izak Snyman at the University of Witwatersrand in Johannesburg, South Africa.
Education / Profile: Master 2 or equivalent. We are seeking motivated students who want to take part
to a state of the art experiment and put some efforts in the theoretical understanding of quantum
simulation using superconducting quantum circuit. This internship can be pursued toward a PhD
Start Period: Flexible
Contact : ROCH Nicolas
Institut Néel - CNRS : phone: +33 4 56 38 71 77 email: [email protected]
Plus d'informations sur : http://neel.cnrs.fr & http://perso.neel.cnrs.fr/nicolas.roch
64
Nouveaux matériaux magnétiques fonctionnels
Les matériaux magnétiques sont à la base de nombreuses applications de hautes technologies que ce
soit dans le domaine du stockage de l’information, de l’électrotechnique (moteurs, détecteur,
actionneurs) ou de l’automobile (véhicules électriques ou hybrides). Ainsi toute amélioration de ces
matériaux se traduit directement par un gain de performance ou peut aussi ouvrir de nouvelles
applications. Récemment cela a aussi permis de mettre à jour de nouveaux matériaux présentant une
forte magnétorésistance, ou même des propriétés magnétocaloriques exceptionnelles ouvrant ainsi de
nouvelles fonctions (stockage d’informations, réfrigération magnétique…). Les recherches se
concentrent sur l’étude de composés associant au moins deux éléments aux propriétés
complémentaires : métal de transition (Fe, Co) et un élément de terre rare. Cela s’est avéré fructueux
pour les matériaux magnétiques durs (aimants) et plus récemment pour les matériaux
magnétocaloriques en conduisant à des matériaux aux propriétés inégalées. Cette démarche doit être
approfondie pour en découvrir de nouveaux, optimiser les propriétés physiques en général et
magnétiques en particulier.
Sujet : Le stage à caractère expérimental comprendra l’étude de nouveaux composés que nous avons
mis à jour et la détermination de leurs propriétés magnétiques macroscopiques ainsi que l’analyse de
leurs propriétés structurales. Les propriétés physiques essentiellement seront déterminées par mesures
magnétiques variées : - mesures d’aimantation en champ fort, - susceptibilité alternative, - analyse
thermomagnétique, - chaleur spécifique. Des mesures diverses (aimantation, résistivité…) seront
effectuées à basses températures (300 à 2K). La compréhension des propriétés physiques originales de
ces nouveaux composés nécessite la connaissance de leur structure. La diffraction des rayons X sera
aussi mise en œuvre en complément.
L’objectif de ce travail est de mettre à jour et comprendre les mécanismes qui régissent les propriétés
de ces matériaux prometteurs.
Interactions et collaborations : Ces études à l’Institut Néel s’appuieront sur et plusieurs
collaborations et internationales existantes (mesures sous pression, études spectroscopiques) au niveau
européen (Allemagne, République Tchèque…) et plus largement mondial (Australie, Canada).
Ce stage pourra se poursuivre par une thèse, il n’est pas limité à un niveau M2R. En effet ce sujet
est au cœur des préoccupations de notre équipe et a vocation à se poursuivre par un doctorat. Dans le
cadre d’un doctorat nous mènerons aussi des études sur les grands instruments n tirnat profit de la
complémentarité entre rayons X et neutrons.
Formation / Compétences nécessaires : M2R ou Ingénieur en Physique des Matériaux. Ce sujet à
caractère expérimental sera l’occasion d’approfondir les connaissances en magnétisme, physique du
solide et cristallographie.
Période envisagée pour le début du stage : février ou mars 2017
Contact : ISNARD Olivier Département PLUM Institut Néel - CNRS : tél 04 76 88 11 46
email [email protected]
65
Investigation of magnetization processes in R-M intermetallic compounds
Introduction : The R-M phases based on rare-earth (R) and transition metals (M) are fascinating
materials from both applied and fundamental viewpoints. Indeed, R-M have led to the first modern
magnets like Sm-Co (SmCo5 and Sm2Co17 type) and latter to the high performance Nd-Fe-B magnets.
Other examples are the (Dy,Tb)Fe2 type Terfenol ® alloys which are by far the best magnetostrictive
materials to date and are widely used in sensors and actuators leading to many applications (Sonar).
Other R-M alloys have also contributed to the development of various techniques such as magnetooptic recording on thin films (Gd-Co). Some compounds are now also considered for new applications
such as spintronic devices (Gd-Co), magnetic refrigeration using magnetocaloric materials (LaFeSi,
RCo2..). The R-M compounds are however complex materials and need fundamental studies to master
their magnetic properties and optimize their performances. Indeed, they are combining two types of
magnetism, the localized magnetic moment originating from the inner 4f electronic shells of the R
element with the delocalized magnetic moments carried by the itinerant 3d electrons of the M
transition metals. Depending upon the atomic concentration one can thus play with different origin of
the magnetization. From a fundamental point of view, the R-M compounds are ideal systems to probe
solid state magnetism since they are presenting a wide range of unusual magnetic behaviour.
and the underlying mechanism involved in
such unusual magnetization process have to be
clarified. The internship will include synthesis
of polycrystalline samples, measurements of
their physical properties (structural and
magnetic) and analysis of the observed
behavior. This will be done in close interaction
with the researchers.
Research to be carried out : Among the
interesting magnetization process that attracted
our attention, we can cite magnetization
reversal in hard magnetic materials exhibiting
promising magnetic properties for permanent
magnet applications. We also recently
discovered the occurence of ultrasharp
magnetization behaviour in LaFe12B6 see
Figure. This manifest itself by unexpected
giant metamagnetic transitions consisting of a
succession of extremely sharp magnetization
steps separated by plateaus. This behavior has
been found at low temperature in LaFe12B6.
This unprecedent behaviour for a purely 3d
itinerant electron system needs to be further
investigated since it presents many remarkable
properties. For instance, under certain
combinations of the external parameters
(temperature and magnetic field), the time
dependence of the magnetization displays an
unusual step-like feature. However, the origin
20
15
B
LaFe12B6
10
E
M (µB/f.u.)
5
A
0
-‐5
C
-‐10
2K
-‐15
D
-‐20
-‐10
-‐8
-‐6
-‐4
-‐2
0
2
4
6
8
10
µ0H (T)
Ongoing collaborations : In the frame of this research work, different collaborations are already
established in particular with the Institute Laue Langevin, as well as Czech collaborators specialists of
magnetic measurements at high pressure. This will be an added value to the project.
This internship is aimed to be followed by a Ph. Thesis
Formation / skills : Master 2 in Solid State Physics or Nanophysics or Engineer in Materials sciences
Starting period foreseen : February or march 2017
Contact : Pr. Olivier ISNARD, Département PLUM Institut Néel - CNRS : tél 04 76 88 11 46
email [email protected] see also : http://neel.cnrs.fr
66
Development of new magnetic actuators for biology applications at the
cellular scale
Cadre général :
The understanding of biological processes at the cellular level requires new tools to study the effect of
localized stimuli on single cells. The interaction between a magnetic field and a magnetic micro-object
(micro/nano-particle, micro-pillar) can remotely produce forces and strain on isolated cells which are
in comparable intensity to biologically relevant forces. For this purpose, it is necessary to design new
magnetic flux sources, at the micron scale, based on various materials to address some of the latest
challenges of cellular biology. In our group, we have developed multiple approaches to produce
micro-sources of magnetic flux[1,2] which were already used for cell sorting and
mechanotransduction studies [3,4]. The next step is to control forces in the piconewton range and local
deformation in the micron range. To be statistically relevant, such experiments need to be repeated
many times, and the ideal device is a highly parallel system where an array of single cells is
collectively excited by an array of micro-magnets.
[1]Dumas-Bouchiat et al. Applied Physics Letters 96,(2010): 102511
[2]Dempsey et al. Applied Physics Letters 104, (2014): 262401
[3]Osman et al. Biomicrofluidics 7,(2013): 54115
[4]Brunet et al. Nature Communications 4 (2013): 2821
Two different systems will be considered. In the
first case, micro-magnets (fig.1) that can be
moved in an external magnetic field, so as to
induce mechanical stress on single cells, will be
developed. In the second case, stationary micromagnets will be developed to apply a very local
force on a single cell, through the attraction of
magnetic nanoparticles either embedded in or
attached to the cell membrane.
The student will take part in the design,
fabrication, characterization and testing of the
micro-magnets.
The
design
will
be
complemented with numerical simulations in Figure 8 : SEM of magnetic micro-pillars produced
order to optimize the dimensioning of the by Deep reactive ion etching followed by Fe
devices and the choice of material. Micro- deposition
fabrication will be carried out with clean room
based lithography/etching/deposition techniques (Nanofab-Neel and PTA-Minatec). After
characterization and testing, the micro-magnets will be integrated into systems for biology studies.
Interaction with biologists and biophysicists at LIPhy (Grenoble) and Institut Curie (Paris) for testing
of the developed devices.
Formation / Compétences : The candidate must have good experimental skills and a master2 in
physics, material science or biophysics
Période envisagée pour le début du stage : Spring 2017
Contact : Devillers Thibaut
Institut Néel - CNRS : tél +33 (0)476887435 e-mail : [email protected]
67
Growth of ferrimagnetic spinels for spin-filtering
General Scope : Spin based electronics take advantage of both
the electron charge and spin in solid-state systems. A crucial
component in applications is the magnetic tunnel junction (MTJ),
where two magnetic layers sandwich a non-magnetic one. Its
conductance depend on the relative spin orientation of the two
electrodes. An alternative way for generating spin-polarized
currents is based on MTJ with magnetic barrier materials, which
results in spin dependent tunneling probabilities (Fig. 1). Efficient
spin-filtering has been demonstrated for ferromagnetic insulators
such as EuS and EuO, which show low transition temperatures.
Spinel ferrites like CoFe2O4 are promising candidates for roomtemperature spin filtering.
Spin based electronics take advantage of both the electron charge
and spin in solid-state systems. A crucial component in
Fig. 1 Schema of spin filtering (J S
applications is the magnetic tunnel junction (MTJ), where two
Moodera et al.,J. Phys.: Condens. Matter
magnetic layers sandwich a non-magnetic one. Its conductance
19 (2007) 165202
depend on the relative spin orientation of the two electrodes. An
alternative way for generating spin-polarized currents is based on
MTJ with magnetic barrier materials, which results in spin
dependent tunneling probabilities (Fig. 1). Efficient spin-filtering
has been demonstrated for ferromagnetic insulators such as EuS
and EuO, which show low transition temperatures. Spinel ferrites
like CoFe2O4 are promising candidates for room-temperature spin
filtering.
We have recently grown epitaxial CoFe2O4(100) films of
nanometric thickness on a Ag(100) substrate and investigated their
structure by in-situ surface x-ray diffraction (SXRD, fig. 2). We
need now to optimize the surface structure and morphology, a
crucial step to get the desired properties. A magnetic electrode - in
our case consisting of magnetite - will be next grown on top to
realize a spin-filtering device. This electrode need to be
Fig. 2 SXRD measurement showing the
magnetically decoupled, which can be realized by the insertion of
epitaxial growth of CoFe2O4(100)/Ag(100)
a magnesium oxide ultrathin layer in-between. Resuming, during
the internship we will study the growth of a
Fe3O4/MgO/CoFe2O4/Ag(100) three-layer.
The lattice constants of each layer of this all oxide system match very-well, which should result in a model
epitaxial MTJ. The samples will be elaborated using a MBE system equipped with several thermal evaporation
sources and the morphology and epitaxy will be studied in-situ by scanning tunneling microscopy (STM) and low
energy electron diffraction (LEED), and ex-situ by XRD. A first characterization of the electronic properties will
be performed with scanning tunneling spectroscopy (STS). Magnetic properties will be further characterized
using x-ray magnetic circular dichroism at the absorption Co and Fe L edges. This second part however is beyond
the scope of the master and can be included in a PhD subject.
Possible collaboration and networking: SIN team (Néel Institut), X. Torrelles, ICMAB (Spain)
Required skills: A good background in condensed matter physics and a strong motivation for
experimental work are required
Starting date: March, 2017
Contact: Maurizio De Santis
Phone:04 76 88 74 13
68
Scanning Josephson Tunneling Microscopy: visualizing bound states in
Superconductors
The ability of electrons to tunnel between two
conductors is extremely sensitive to both distance
and density of states. This has made scanning
tunneling microscopy/spectroscopy (STM/STS) an
extremely sensitive and versatile tool to visualize
atomic scale topographic features and variations in
the local density of states. When both conductors
(that is, tip and sample) are superconducting, the
tunneling of Cooper pairs can be even more
sensitive to the sample’s electronic properties, an
effect which has recently led to exciting
discoveries. The target of this Master/PhD project
is to implement the Scanning Josephson Tunneling
Microscopy (SJTM) technique in our laboratory.
Nanometer scale scatterers (single atom, molecule,
quantum dot) can interact with the superconducting
condensate via potential scattering and/or magnetic
exchange coupling. This can lead to bound states at
energies below the superconducting gap with
peculiar spatial and spectral properties.
Using SJTM we will investigate the
interplay of superconductivity to with such
local perturbations, as a function of
magnetic field and an external gate potential.
Figure 1: Local density of states map around
magnetic adatom on Pb and sketch of STM
experiment using superconducting tip.
This project will be carried out using a low temperature STM operating at 100 mK, at Institut Néel [1].
Part of the experiments will be performed in the group of K. Franke (Berlin), in a low temperature
STM with complementary capabilities [2]. The student’s work will encompass:
- Clean-room nanofabrication (substrates for impurity gate control, superconducting tips)
- Ultra-low noise electronics development (current bias to a high impedance junction)
- Low temperature, scanning probe and ultra-high vacuum techniques
- Theoretical analysis and interpretation
[1] Charge Puddles in Graphene Near the Dirac Point, S. Samaddar, I. Yudhistira, S. Adam, H. Courtois, and C.B.
Winkelmann, Phys. Rev. Lett. 116, 126804 (2016).
[2] Magnetic anisotropy in Shiba bound states across a quantum phase transition, N. Hatter, B.W. Heinrich, M. Ruby, J.I.
Pascual, K.J. Franke, Nature Comm. 6, 8988 (2015).
This project will be carried out in collaboration with the group of K. Franke (Berlin). Experiments will
be carried out at both locations. At both locations, analysis and interpretation will benefit from strong
local theoretical support (D. Basko / Grenoble, F. von Oppen / Berlin).
Ce stage pourra se poursuivre par une thèse (ou ce sujet est limité à un stage M2...).
Yes
Master in Physics
Période envisagée pour le début du stage : beginning of 2017
Contact : Winkelmann Clemens / Courtois Hervé
Institut Néel - CNRS : 04 76 88 78 36
[email protected]
69
Model hard-soft magnetic nanocomposites
Cadre général :
Rare earth - transition metal (RE-TM) magnets play an important and growing role in the clean energy
sector, being key components of hybrid electric vehicles and gearless wind turbines. The growth in the
room temperature energy product of permanent magnets, which doubled in value every 18 years in the
last century, has been practically stagnant over the last 20 years. This is because no new magnetic
phases having intrinsic properties better than those of today’s best material, Nd2Fe14B, have been
discovered. Kneller and Hawig proposed an elegant approach to further increase the energy product of
magnets using known materials, by producing a nano-structured composite material that combines a
hard magnetic phase exchange coupled to a high magnetisation soft phase [1]. Such nanocomposites
would also reduce the overall RE content of the magnet, which is very important in light of recent
concerns with the sourcing and pricing of RE elements. While much effort has gone into producing
hard/soft nanocomposites, no studies reported significantly enhanced energy products because of
insufficient control over the nanostructure, in particular the size of the soft phase grains and the
crystallographic texture of the hard phase grains.
The student will develop and study model
hard/soft nanocomposites with an
unprecedented level of control over the
sample nanostructure. Nano-lithography
will be used to fabricate arrays of FeCo
nano-rods of controlled size, shape,
position and overall surface content.
Sputtering will be used to fabricate a highly
coercive NdFeB hard magnetic matrix [2].
Structural characterization will be carried out
using X-Ray diffraction, Atomic Force
Microscopy, Scanning and Transmission
Electron Microscopy.
Figure 1 : SEM / MFM images of FeCo nanolithographically patterned rods.
Magnetic characterization will be carried out using VSM-SQUID magnetometry, Magnetic Force
Microscopy under field, Scanning Magneto-Optic magnetometry and possibly X-ray Magnetic
Circular Dichroism.
[1] E. F. Kneller, & R. Hawig, IEEE Trans. Magn. 27(1991) 3588
[2] N.M. Dempsey, T.G. Woodcock, et al., Acta. Mat. 61 (2013) 4920
The student will work closely with a post-doc at Institut Néel on sample preparation and
characterisation, in the framework of an ANR project involving three other labs (SPCTS-Limoges,
ILM-Lyon and the ESRF).
Formation / Compétences : The candidate must have good experimental skills and a master2 in
physics or material science.
Période envisagée pour le début du stage : Spring 2017
Contact : DEMPSEY Nora
Institut Néel - CNRS : tél +33 (0)476887435 e-mail : [email protected] Plus d'informations
sur : http://neel.cnrs.fr
70
Plasmonic response of copper nanoparticles during their growth on TiO2
General Scope:
Noble metal Au, Ag and Cu nanoparticles (NPs) have the unique ability to absorb visible
(ViS) part of the electromagnetic field due to the resonance with a collective oscillation of
their conduction electrons (fig. 1). This excitation is called localized surface plasmon
resonances (LSPR).
It has been very recently shown that LSPR can strongly enhance the catalytic activity under
visible-light and act as a photocatalyst. The involved mechanisms are under debate. The
understanding of the plasmonic assisted photocatalysis is an important issue since it opens a
new way allowing to overcome the limit of conventional Semi-Conductor mainly active in
ultra-violet (UV).
In this context of photocatalysis, Cu is of a particular interest because of its chemical activity,
it is also the most abundant and the cheapest noble metals.
The internship will be devoted to the study of the plasmonic response of copper nanoparticles
during their growth on a TiO2 crystal.
The aim is to correlate the structural
properties with the optical ones.
The setup which will be used is shown on
the picture (2). The nanoparticles are
grown by molecular beam epitaxy in an
ultra-high vacuum chamber. Their optical
response are measured by Surface
Differential Reflectivity Spectroscopy
(SRDS). It consists to measure the relative
variation of the reflectance under UV-Vis
light during copper deposition compared to
the bare substrate (3).
INSP paris, IRCE Lyon
Possible extension as a PhD: oui
Required skills:
This subject is intended has students having physicist's training and/or in nanosciences
Starting date: avril 2017
Contact:
Name: SAINT-LAGER Marie-Claire
Phone:04 76 88 74 15
71
Mixed order phase transition
Cadre général :
The general framework is the lattice statistical mechanics, more precisely the study of phase
transitions.
The purpose of the internship is to study a lattice model recently proposed by D. Mukamel.
This model has the property to have both a jump in the magnetization and a diverging correlation
length. This is a very peculiar situation since usually a jump in the order parameter is a landmark of
first order transition, while a diverging correlation length characterizes second order phase transition.
This result is an exact result, free of any approximation. The goal of this work is to study the finite
size effect in this system. Firstly it will be necessary to understand the result shown in the above
mentioned paper, then to get some intuition to determine the size effect for such systems.
A part of the work being numerical, the computing power of the Institut Néel will be used.
This work is a part of an ongoing collaboration with hungarian physicists from Budapest (Hungary)
A priori no.
Beside knowing the first results in lattice statistical physics (eg Ising model) Interest and skills in
computational physics is needed for this internship.
Période envisagée pour le début du stage : anytime
Contact : Anglès d’Auriac
Institut Néel - CNRS : 04 76 88 78 42 mel [email protected]
72
Listening to the noise of a four-terminal Josephson junction
Introduction : In the Josephson effect, a
nondissipative supercurrent flows through a phasebiased weak link between two superconductors. The
Josephson effect is one of the most important building
block of quantum nanoelectronic circuits. In our group,
we study more specifically more complex Josephson
junctions with three or four terminals (see the figure
for a three-terminal
Josephson junction). A recent experiment [1] provided
evidence for quantum fluctuations of the current (e.g.
current noise) in a three-terminal Josephson junction. The internship will be about calculations of the
current noise in a four-terminal Josephson junction consisting of three superconductors and one
normal lead. Those four-terminal Josephson junctions may offer the opportunity to provide
information on the number of Cooper pairs participating to a single current-carrying quantum process
(the so-called effective charge).
[1] Y. Cohen, Y. Ronen, J.-H. Kang, M. Heiblum, D. Feinberg, R. Mélin and H. Shtrikman, submitted
to Science, https://arxiv.org/abs/1606.08436
Proposed work-program : The noise in those four-terminal junctions is expected to originate from
the exchange between pairs (from the superconducting leads) and normal electrons (in the normal
leads). It is expected that the student will provide information on the interest of making those
experiments in the next years. The intership will consist of analytical Green’s function calculations for
the average current and noise in a four-terminal Josephson junction.
Interactions and possible collaborations : This project is within the framework of national and
international collaborations that we have been developping over the last years. It is expected that the
student should interact on a daily basis with the other members of our group in Grenoble (Serge
Florens and Denis Feinberg who is developping Nazarov’s circuit theory calculations for similar setups), as well as with our close collaborator Benoît Douçot in Jussieu. The student is expected to visit
the experiment of François Lefloch in CEA-Grenoble. This work is also within an on-going
collaboration with the experimental group of Moty Heiblum at the Weizmann Institute in Israël. Both
of those experiments can measure (in different regimes) the noise which will be calculated during the
internship.
The intership can be followed by a PhD thesis.
Required skills : It is expected that the student should master well the main ideas of his M2 advanced
course on Quantum Mechanics.
Period for the internship : Anytime during academic year 2016-2017
Contact : Régis Mélin
Institut Néel - CNRS 04-76-88-11-88, [email protected]
73
Systèmes Hybrides Spin-Nanorésonateurs mécaniques
Le refroidissement et l’observation d’un oscillateur mécanique
macroscopique dans son état quantique fondamental, réalisé en
2010-2011 dans plusieurs laboratoires, permet maintenant
d’envisager la génération d’états mécaniques non-classiques.
Pour ce faire une stratégie consiste à coupler ce résonateur
mécanique ultrafroid à un autre système quantique, un qubit, dans
le but de transférer sa nature quantique à l’oscillateur. Ce faisant
on réalise un système hybride mécanique couplant les deux
briques de bases de la mécanique quantique [1,2].
Le groupe de recherche Nano-optomécanique quantique hybride de l’Institut Néel explore une voie
dans laquelle des nanofils de carbure de silicium sont couplés au spin électronique d’un centre coloré
du diamant, le centre NV (pour Nitrogen-Vacancy). Une première expérience de principe [1] a permis
de développer ce système hybride spin-oscillateur: un centre coloré hébergé dans un nanocrystal de 50
nm de diamètre a été déposé à l’extrémité d’un nanofil de SiC. En immergeant le système dans un très
fort gradient de champ magnétique, par effet Zeeman le spin du centre coloré est couplé à la position
de l’oscillateur. On a pu ainsi montrer que les vibrations de l’oscillateur sont encodées sur le spin
électronique. Ce projet vise à explorer de nouveaux mécanismes de couplage dans ces systèmes
hybrides et à étudier le couplage spin-oscillateur en sens inverse, c'est-à-dire d’encoder l’état du spin
électronique sur la position de l’oscillateur, reproduisant ainsi l’expérience de Stern et Gerlach avec
des objets macroscopiques.
Pour ce faire, une sensibilité en force extrême est requise car la force exercée par le spin sur
l’oscillateur est de l’ordre de ~20 aN pour un gradient de 1e6 T/m. De tels niveaux de sensibilité sont
accessibles avec des oscillateurs mécaniques de très faible masse, comme démontré à température
ambiante sur les nanofils de SiC [2]. De même, il est nécessaire de lire avec une grande précision les
vibrations de ces nanofils. Les travaux en cours au laboratoire démontrent que la lecture optique des
vibrations de nanofils permet de résoudre avec une grande dynamique leur mouvement Brownien.
Enfin des protocoles avancés de manipulation du spin électronique ont également été mis en œuvre [3]
au laboratoire qui ont permis de mettre en évidence la synchronisation du spin sur la vibration
mécanique [5]. On a ainsi pu observer l’analogue phononique du triplet de Mollow en
électrodynamique quantique, apparaissant lorsque le qubit de spin est fortement excité par les
vibrations du nanofil.
[1] O. Arcizet et al, Nature Physics 7, 879 (2011).
[2] A. Gloppe et al, Nature Nanotechnology (2014).
[3]S. Rohr et al., PRL 112, 010502 (2014)
[4] B. Pigeau et al, Nature Communications ( 2015).
[5] L. Mercier de Lépinay et al., arXiv:1503.03200 (2015).
Interactions et collaborations : NEEL, ENS Cachan, labo. Kastler Brossel, Uni-Basel.
Ce stage pourra se poursuivre par une thèse
Formation / Compétences : Ce travail de thèse permettra d’acquérir un savoir-faire en nano-optique,
en nanosciences et en manipulation de système quantiques. Même si ce projet revêt un fort caractère
expérimental, l’aspect novateur des systèmes hybrides nanomécaniques requiert un intérêt poussé pour
la formalisation théorique.
Contact : Arcizet Olivier- Benjamin Pigeau, Institut Néel - CNRS : 04 76 88 12 43
[email protected] [email protected] Plus d’info. sur : http://neel.cnrs.fr
74
Electric field manipulation of skyrmions
General Scope:
Downscaling magnetic film thickness to the nanometer range allows to evidence new lengthscales.
New physical effects are enhanced and dominate the usual effects. Nanomagnetism is the research
field where these new behaviours are studied. Due to the constant need for larger and larger
information storage and information processing densities, such fundamental studies are associated to
the development of new magnetic devices (sensors, memories, oscillators …).
Downsizing the lateral size of structures, allows for the study of isolated magnetic entities such as
single magnetic domains, or individual magnetic domains walls. The ultimate magnetic domain could
take the shape of a skyrmion structure, which is a topologically stabilised nano-object, where a non
collinear interaction (the Dzyaloshinskii-Moriya interaction) plays a crucial role. The existence of
such an isolated object in an ultra-thin metallic ferromagnetic film has been speculated for the last few
years. Finally, the creation and manipulation of such a skyrmion bubble using an applied magnetic
field or a spin-polarised current has recently been published (W. Jiang et al. Science July 2015).
In 2016 we have demonstrated in our researche group the reproducible and controled nucleation and
annihilation of skyrmions using electric field gating, an energy efficient and easily integrable solution.
These results constitute an important step toward the use of skyrmions in functional magnetic devices.
The aim this work is to further use electric gating to control the position of the nucleated skyrmions.
For that the skyrmion will be displaced using an electric current and the electric field will be used to
stop or allow the skyrmion propagation.
The environment will be the micro and nanomagnetism (MNM) research group of Institut Néel. with
interactions with the Deposition, Magnetometry and Nanofab technical groups. The student will work
together with a third year PhD student working on a close subject. The student can possibly
continue the subject in the framework of a PhD starting in 2017.
Possible extension as a PhD:yes
Required skills: Solid state physics with a taste for experimental studies. Interest for fabricating
magnetic model systems, detailed studies and quantitative modeling.
Starting date: spring 2017
Contact:
Name: Anne Bernand-Mantel, Laurent Ranno
e-mails: [email protected], [email protected]
75
Non-equilibrium quantum modeling of nano-structure based solar cells
Cadre général :
Nowadays, because of growing energy demand, exhaustion of oil resources, and global warming
issues, the world is in need of alternative energy sources. Solar energy is one of the clean, renewable
and available energy sources and great attention is given to new solar cells concepts based in particular
on nanostructures or molecular systems.
The development of new type of solar cells requires an accurate, reliable and comprehensive
simulation of the designed structures. Theoretical modeling of such systems has been a challenging
task for several years and we have developed a new simple non-equilibrium quantum formalism. This
approach can be applied to two level models of photo-cells (see figure) and current efforts includes its
application to more realistic models of molecular photocells or quantum dots. During its internship the
student will learn basic aspects of the formalism which relies on the quantum scattering theory. He
/she will participate to comprehensive simulation for simple models of nanosized solar cells. The
student must be able to use Fortran codes. Computational ressources are available at Institut Néel.
Figure 1: Two level model. The photon is absorbed in the central part (molecule/ quantum dot) and
creates an electron in the upper level and a hole in the lower level. The electron (hole) can be
evacuated through the right (left) lead. The net result of the absorption of a photon is the transfer of an
electron from the left to the right lead.
Currently, we have strong collaborations with scientific groups from Canada, USA and Iran.
The formalism developed in the team is new and opens an active area for several years. The student
can continue this subject as a PhD thesis.
Quantum mechanics - Programming and analysis skills and having teamwork abilities.
Période envisagée pour le début du stage : March or April 2017
Contact : Mayou Didier
Institut Néel - CNRS : Tel : 04 76 88 74 66 mel : [email protected]
76
NOTES
77

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