Sommaire - Triangle de la Physique

Transcription

PUBLICATIONS
PROJETS 2008
Sommaire
[2008-002T] EEES .................................................................................................................................................. 7
Excited electron dynamics in Cu nanowires supported on a Cu(111) surface .................................................... 7
Extraordinary Electron Propagation Length in a Metallic Double Chain Supported on a Metal Surface ........... 7
Mapping of the electron transmission through the wall of a quantum corral ...................................................... 7
[2008-005T] EXTREME ........................................................................................................................................ 8
A microscopic view on the Mott transition in chromium-doped V2O3 .............................................................. 8
[2008-007T] QCCM ............................................................................................................................................... 9
Binary and ternary recombination of D-3(+) ions with electrons in He-D-2 plasma .......................................... 9
Binary and ternary recombination of H-3(+) and D-3(+) ions with electrons in low temperature plasma.......... 9
Calculation of rate constants for vibrational and rotational excitation of the H+(3) ion by electron impact .... 10
Optical phase and the ionization-dissociation dynamics of excited H2 ............................................................ 10
Assignment of resonances in dissociative recombination of HD(+) ions: High-resolution measurements
compared with accurate computations .............................................................................................................. 10
Electron collisions with BF+: bound and continuum states of BF .................................................................... 11
Formation of the simplest stable negative molecular ion H3- in interstellar medium ....................................... 11
Laser control of complete vibrational transfer in Na2 using resonance coalescence ........................................ 11
Laser cooling of the vibrational motion of Na(2) combining the effects of zero-width resonances and
exceptional points ............................................................................................................................................. 12
Photoassociation of a cold-atom-molecule pair. II. Second-order perturbation approach ................................ 12
Proposal for a Laser Control of Vibrational Cooling in Na-2 Using Resonance Coalescence .......................... 12
Triplet-singlet conversion in ultracold Cs-2 and production of ground-state molecules ................................... 13
Breaking a tetrahedral molecular ion with electrons: study of NH4+ ............................................................... 13
Potential energy and dipole moment surfaces of HCO- for the search of H- in the interstellar medium .......... 13
Photoassociation of a cold-atom-molecule pair: Long-range quadrupole-quadrupole interactions .................. 14
Cold atom-molecule photoassociation: long-range interactions beyond the 1/Rn expansion ........................... 14
Laser cooling of the vibrational motion of Na2 combining the effects of Zero Width Resonances and
Exceptional Points. ............................................................................................................................................ 14
Long-range interactions between ultracold atoms and molecules including atomic spin-orbit ......................... 15
Photoassociation of a cold atom-molecule pair II: second-order perturbation approach .................................. 15
Potential energy and dipole moment surfaces of HCO- for the search of H- in the interstellar medium .......... 15
Theory of dissociative recombination of a linear triatomic ion with permanent electric dipole moment: Study
of HCO+............................................................................................................................................................ 16
[2008-015T] ULYSSE & [2009-004T] ULYSSE II ............................................................................................. 16
Insight into low frequency noise induced by gate leakage current in AlGaAs/GaAs high electron mobility
transistors at 4.2 K ............................................................................................................................................ 16
Input Noise Voltage Below 1 nV/Hz(1/2) at 1 kHz in the HEMTs at 4.2 K ..................................................... 16
The Role of the Gate Geometry for Cryogenic HEMTs: Towards an Input Voltage Noise Below 0.5 nV/root
Hz at 1 kHz and 4.2 K ....................................................................................................................................... 17
28/02/2013
1
PUBLICATIONS
PROJETS 2008
[2008-016T] SMGM ............................................................................................................................................. 17
Elementary excitation modes in a granular glass above jamming ..................................................................... 17
[2008-019T] MCQM............................................................................................................................................. 18
Multiple-measurement Leggett-Garg inequalities ............................................................................................. 18
Implementation of a Nondeterministic Optical Noiseless Amplifier ................................................................ 18
Nondeterministic noiseless amplification of optical signals: a review of recent experiments .......................... 18
[2008-020T] MICROHALL.................................................................................................................................. 19
A local noise measurement device for magnetic physical systems ................................................................... 19
[2008-025T] FLUCT-DMABN............................................................................................................................. 19
Do fluorescence and transient absorption probe the same intramolecular charge transfer state of 4(dimethylamino)benzonitrile? ........................................................................................................................... 19
Intramolecular charge transfer and dual fluorescence of 4-(dimethylamino) benzonitrile: ultrafast branching
followed by a two-fold decay mechanism ......................................................................................................... 19
[2008-026T] Prodymag ......................................................................................................................................... 20
Dynamic fluctuations and two-dimensional melting at the spin reorientation transition .................................. 20
[2008-027T] POMICO .......................................................................................................................................... 20
Organization of Block Copolymers using NanoImprint Lithography: Comparison of Theory and Experiments
.......................................................................................................................................................................... 20
Tailoring Nanostructures Using Copolymer Nanoimprint Lithography ........................................................... 21
Block Copolymer at Nano-Patterned Surfaces .................................................................................................. 21
[2008-028T] MASLOV ........................................................................................................................................ 21
Nonanalytic Spin Susceptibility of a Fermi Liquid: The Case of Fe-Based Pnictides ...................................... 21
[2008-029T] HY-IRGS-2 ...................................................................................................................................... 22
Emergence of Rigidity at the Structural Glass Transition: A First-Principles Computation ............................. 22
Replica theory of the rigidity of structural glasses ............................................................................................ 22
[2008-031T] STOLTE .......................................................................................................................................... 23
Unusual Quantum Interference in the S-1 State of DABCO and Observation of Intramolecular Vibrational
Redistribution .................................................................................................................................................... 23
[2008-032T] B-DIAMANT .................................................................................................................................. 23
Influence of a static magnetic field on the photoluminescence of an ensemble of nitrogen-vacancy color
centers in a diamond single-crystal ................................................................................................................... 23
Avoiding power broadening in optically detected magnetic resonance of single NV defects for enhanced dc
magnetic field sensitivity .................................................................................................................................. 24
[2008-046T] DYNELEC ....................................................................................................................................... 24
Ion Pair Formation in Multiphoton Excitation of NO2 Using Linearly and Circularly Polarized Femtosecond
Light Pulses: Kinetic Energy Distribution and Fragment Recoil Anisotropy ................................................... 24
Molecular frame photoemission in dissociative ionization of H-2 and D-2 induced by high harmonic
generation femtosecond XUV pulses ................................................................................................................ 25
[2008-047T] GAIN ............................................................................................................................................... 25
Enhanced photoluminescence of heavily n-doped germanium ......................................................................... 25
28/02/2013
2
PUBLICATIONS
PROJETS 2008
Band structure and optical gain of tensile-strained germanium based on a 30 band k center dot p formalism . 26
Control of direct band gap emission of bulk germanium by mechanical tensile strain ..................................... 26
Direct and indirect band gap room temperature electroluminescence of Ge diodes ......................................... 26
Control of tensile strain in germanium waveguides through silicon nitride layers ........................................... 27
[2008-048T] SPECTMAG .................................................................................................................................... 27
Atomic structure of tip apex for spin-polarized scanning tunneling microscopy .............................................. 27
[2008-051T] PHOTO-MAG ................................................................................................................................. 28
Controlled growth of core@shell heterostructures based on Prussian blue analogues...................................... 28
Magnetic Core-Shell Nanoparticles from Nanoscale-Induced Phase Segregation ............................................ 28
Influence of Protected Annealing on the Magnetic Properties of gamma-Fe2O3 Nanoparticles ...................... 29
[2008-052T] ACOUSTIC ..................................................................................................................................... 29
Homogeneous broadening of the S to P transition in InGaAs/GaAs quantum dots measured by infrared
absorption imaging with nanoscale resolution .................................................................................................. 29
[2008-053T] SERPBIO ......................................................................................................................................... 30
First observation in the gas phase of the ultrafast electronic relaxation pathways of the S-2 states of heme and
hemin................................................................................................................................................................. 30
Strength of (NHS)-S-Hydrogen Bonds in Methionine Residues Revealed by Gas-Phase IR/UV Spectroscopy
.......................................................................................................................................................................... 30
[2008-053T] SERPEBIO & [2010-003T] COMOVA .......................................................................................... 31
Unraveling the Mechanisms of Nonradiative Deactivation in Model Peptides Following Photoexcitation of a
Phenylalanine Residue ...................................................................................................................................... 31
[2008-054T] SYMTCOB ...................................................................................................................................... 31
Growth and characterisation of Li(x)CoO(2) single crystals ............................................................................ 31
Na-23 NMR study of sodium order in NaxCoO2 with 22 K Neel temperature ................................................ 32
[2008-055T] GRAMINE ....................................................................................................................................... 32
Conductive-probe AFM characterization of graphene sheets bonded to gold surfaces..................................... 32
[2008-056T] FLAG ............................................................................................................................................... 33
Anatomy of a femtosecond laser processed silica waveguide [Invited] ............................................................ 33
Dependence of the femtosecond laser refractive index change thresholds on the chemical composition of
doped-silica glasses ........................................................................................................................................... 33
Modification thresholds in femtosecond laser processing of pure silica: review of dependencies on laser
parameters [Invited] .......................................................................................................................................... 33
Time-resolved plasma measurements in Ge-doped silica exposed to infrared femtosecond laser .................... 34
Gold Nanoparticles Reshaped by Ultrafast Laser Irradiation Inside a Silica-Based Glass, Studied Through
Optical Properties .............................................................................................................................................. 34
Oriented creation of anisotropic defects by IR femtosecond laser scanning in silica ....................................... 34
Three-dimensional photoprecipitation of oriented LiNbO3-like crystals in silica-based glass with femtosecond
laser irradiation ................................................................................................................................................. 35
[2008-057T] PAO ................................................................................................................................................. 35
Dielectric gratings for wide-angle, broadband absorption by thin film photovoltaic cells................................ 35
28/02/2013
3
PUBLICATIONS
PROJETS 2008
Optical Patch Antennas for Single Photon Emission Using Surface Plasmon Resonances .............................. 35
Experimental study of hot spots in gold/glass nanocomposite films by photoemission electron microscopy .. 36
Nanoscale magnetic field mapping with a single spin scanning probe magnetometer...................................... 36
[2008-058T] FemtoARPES ................................................................................................................................... 36
Coherent Phonon Coupling to Individual Bloch States in Photoexcited Bismuth ............................................ 36
Giant Anisotropy of Spin-Orbit Splitting at the Bismuth Surface ..................................................................... 37
Ultrafast Surface Carrier Dynamics in the Topological Insulator Bi2Te3 ........................................................ 37
Ultrafast filling of an electronic pseudogap in an incommensurate crystal ....................................................... 38
[2008-060T] MeMoFri .......................................................................................................................................... 38
Contact Angle and Contact Angle Hysteresis Measurements Using the Capillary Bridge Technique ............. 38
Incidence of the molecular organization on friction at soft polymer interfaces ................................................ 38
Synthesis of well-defined poly(dimethylsiloxane) telechelics having nitrobenzoxadiazole fluorescent chainends via thiol-ene coupling ............................................................................................................................... 39
Wetting and Dewetting Transition: An Efficient Toolbox for Characterizing Low-Energy Surfaces .............. 39
[2008-061T] MINIATOM .................................................................................................................................... 40
Light-pulse atom interferometry in microgravity .............................................................................................. 40
Frequency doubled 1534nm laser system for potassium laser cooling ............................................................. 40
[2008-062T] DYNANEX...................................................................................................................................... 40
Photoionization of 2-pyridone and 2-hydroxypyridine ..................................................................................... 40
A two-step ICT process for solvatochromic betaine pyridinium revealed by ultrafast spectroscopy,
multivariate curve resolution, and TDDFT calculations ................................................................................... 41
Femtosecond dynamics of cyclopropenylidene, c-C3H2 .................................................................................. 41
[2008-063T] SAMNANO ..................................................................................................................................... 42
UPS, XPS, and NEXAFS Study of Self-Assembly of Standing 1,4-Benzenedimethanethiol SAMs on Gold . 42
[2008-064T] THERMETG.................................................................................................................................... 42
Relevance of visco-plastic theory in a multi-directional inhomogeneous granular flow .................................. 42
Experimental Evidence of a Phase Transition in a Closed Turbulent Flow ...................................................... 43
Susceptibility divergence, phase transition and multistability of a highly turbulent closed flow ..................... 43
[2008-065T] Glasdespin........................................................................................................................................ 44
Magnetic order in Tb2Sn2O7 under high pressure: From ordered spin ice to spin liquid and antiferromagnetic
order .................................................................................................................................................................. 44
Field evolution of the magnetic structures in Er2Ti2O7 through the critical point ........................................... 44
Field-induced magnetic structures in Tb2Ti2O7 at low temperatures: From spin-ice to spin-flip structures ... 44
Neutron diffraction study of the chiral magnet MnGe ...................................................................................... 45
[2008-066T] OXY SPINTRONICS ...................................................................................................................... 45
Towards Two-Dimensional Metallic Behavior at LaAlO3/SrTiO3 Interfaces ................................................. 45
Ferroelectric Control of Spin Polarization ........................................................................................................ 46
Giant tunnel electroresistance with PbTiO3 ferroelectric tunnel barriers ......................................................... 46
Interface-induced room-temperature multiferroicity in BaTiO(3) .................................................................... 46
28/02/2013
4
PUBLICATIONS
PROJETS 2008
Restoration of bulk magnetic properties by strain engineering in epitaxial CoFe(2)O(4) (001) ultrathin films 47
Ultrathin oxide films and interfaces for electronics and spintronics ................................................................. 47
[2008-067T] CLEL ............................................................................................................................................... 48
Seed level requirement for improving the temporal coherence of a Free-Electron Laser ................................. 48
[2008-070T] LongWave........................................................................................................................................ 48
In Situ Generation of Surface Plasmon Polaritons Using a Near-Infrared Laser Diode ................................... 48
[2008-071T] PSYCHE .......................................................................................................................................... 49
Addition of Si-Containing Gases for Anisotropic Etching of III-V Materials in Chlorine-Based Inductively
Coupled Plasma................................................................................................................................................. 49
High-aspect-ratio inductively coupled plasma etching of InP using SiH4/Cl-2: Avoiding the effect of electrode
coverplate material ............................................................................................................................................ 49
[2008-072T] POMS .............................................................................................................................................. 50
A PGSE-NMR Study of Molecular Self-Diffusion in Lamellar Phases Doped with Polyoxometalates ........... 50
Communications: Short-range dynamics of a nematic liquid-crystalline phase................................................ 50
Orientational Order of Colloidal Disk-Shaped Particles under Shear-Flow Conditions: a Rheological-SmallAngle X-ray Scattering Study ........................................................................................................................... 50
[2008-075T] Magnetic-Graphene ......................................................................................................................... 51
Spin-flip excitations, spin waves, and magnetoexcitons in graphene Landau levels at integer filling factors .. 51
The magnetic field particle-hole excitation spectrum in doped graphene and in a standard two-dimensional
electron gas ....................................................................................................................................................... 51
Theory of Bernstein modes in graphene............................................................................................................ 52
[2008-080T] GEOFLOW ...................................................................................................................................... 52
Viscous spreading of an inertial wave beam in a rotating fluid ........................................................................ 52
Direct Measurements of Anisotropic Energy Transfers in a Rotating Turbulence Experiment ........................ 52
Excitation of inertial modes in a closed grid turbulence experiment under rotation ......................................... 53
CHEMO-hydrodynamic coupling between forced advection in porous media and self-sustained chemical
waves................................................................................................................................................................. 53
Earth rotation prevents exact solid-body rotation of fluids in the laboratory .................................................... 54
Inertial waves and modes excited by the libration of a rotating cube ............................................................... 54
Relation between first arrival time and permeability in self-affine fractures with areas in contact .................. 54
Stokes flow paths separation and recirculation cells in X-junctions of varying angle ...................................... 55
[2008-082T] NonFermiSupra................................................................................................................................ 55
Hund's coupling and its key role in tuning multiorbital correlations................................................................. 55
Janus-Faced Influence of Hund's Rule Coupling in Strongly Correlated Materials .......................................... 56
Role of oxygen-oxygen hopping in the three-band copper-oxide model: Quasiparticle weight, metal insulator
and magnetic phase boundaries, gap values, and optical conductivity.............................................................. 56
Covalency, double-counting, and the metal-insulator phase diagram in transition metal oxides ...................... 56
Path to poor coherence in the periodic Anderson model from Mott physics and hybridization........................ 57
[2008-086T] XDIF ................................................................................................................................................ 57
Single-shot Femtosecond X-Ray Holography Using Extended References ...................................................... 57
28/02/2013
5
PUBLICATIONS
PROJETS 2008
[2008-088T] OPODRAG ...................................................................................................................................... 58
Stimulated Raman scattering in an optical parametric oscillator based on periodically poled MgO-doped
stoichiometric LiTaO3 ...................................................................................................................................... 58
Frequency stabilization at the kilohertz level of a continuous intracavity frequency-doubled singly resonant
optical parametric oscillator .............................................................................................................................. 58
Diode-pumped Pr:BaY(2)F(8) continuous-wave orange laser .......................................................................... 58
Sub-kHz-level relative stabilization of an intracavity doubled continuous wave optical parametric oscillator
using Pound-Drever-Hall scheme ..................................................................................................................... 59
Optimization of the resonant wave output coupling of a singly resonant optical parametric oscillator using an
intracavity plate ................................................................................................................................................. 59
Ultranarrow resonance due to coherent population oscillations in a Lambda-type atomic system ................... 59
[2008-091T] CAAS............................................................................................................................................... 60
Anisotropic magneto-resistance in a GaMnAs-based single impurity tunnel diode: A tight binding approach 60
Spin splitting of electron states in (110) quantum wells: Symmetry analysis and k.p theory versus microscopic
calculations........................................................................................................................................................ 60
[2008-091T] CAAS 1 & [2012-019T] CAAS 2 .................................................................................................... 61
Anomalous suppression of valley splittings in lead salt nanocrystals without inversion center ....................... 61
[2008-092T] ALVAREZ....................................................................................................................................... 61
Nanostructured tantalum nitride films as buffer-layer for carbon nanotube growth ......................................... 61
[2008-095T] STP .................................................................................................................................................. 62
Electrical transport properties of Mn-doped LaFeAsO oxypnictide ................................................................. 62
Bi1-xSrxCuSeO oxyselenides as promising thermoelectric materials .............................................................. 62
Effects of Co doping on the transport properties and superconductivity in CeFe1-xCoxAsO .......................... 62
Electrical transport properties of F-doped LaFeAsO oxypnictide ..................................................................... 63
Electronic phase diagram of NdFe1-xRhxAsO ................................................................................................. 63
Superconductivity at 15 K in NdFe0.9Rh0.1AsO without F-doping ................................................................ 63
28/02/2013
6
PUBLICATIONS
PROJETS 2008
[2008-002T] EEES
Porteur : Jean-Pierre Gauyacq
Axe B
Excited electron dynamics in Cu nanowires supported on a Cu(111)
surface
Article publié en 2009
Auteurs : Diaz-Tendero S, Olsson FE, Borisov AG, Jean-Pierre Gauyacq
Réf. : PHYSICAL REVIEW B 79 (2009) 115438
We present a theoretical study of the excited electron dynamics in infinite Cu monoatomic chains (nanowires)
supported on a Cu(111) surface. A joint approach based on the wave packet propagation and the density
functional theory is used. The nanowire-induced potential obtained from ab initio density functional theory
calculations serves as an input for the wave-packet propagation study of the excited electron dynamics. The
energy dispersion and the lifetime of an unoccupied one-dimensional (1D) nanowire-localized electronic band
with sp character are obtained. From the group velocity and lifetime of the 1D sp-band states, it follows that an
excited electron can travel about four to five atomic sites along the nanowire before its escape into the bulk. We
show that the surface projected band gap and the surface Brillouin zone backfolding of the substrate states play a
fundamental role in the lifetime of the nanowire-localized states.
Extraordinary Electron Propagation Length in a Metallic Double
Chain Supported on a Metal Surface
Auteurs : Diaz-Tendero S, Borisov AG, Jean-Pierre Gauyacq
Réf. : PHYSICAL REVIEW LETTERS 102 (2009) 166807
PRB 83 (2011) 115453
The present theoretical study shows that a double chain of Cu metal atoms adsorbed on a Cu(111) metal surface
can guide an excited electron for distances exceeding 10 nm. The nanostructure appears to be quasi-decoupled
from the substrate and thus to act as a nanowire. The origin of the above phenomenon is the interference between
the decay of the quasistationary 1D sp-band states localized on each chain. This allows to approach the situation
of the formation of bound states in the continuum first discussed in quantum systems by von Neumann and
Wigner.
Mapping of the electron transmission through the wall of a
quantum corral
Auteurs : Gauyacq, JP. Diaz-Tendero, S. Borisov, AG
Réf. : SURFACE SCIENCE 603 (2009) 2074-2081
We report on a theoretical study of the escape of confined surface states electrons from quantum corrals made of
Cu adatoms on a Cu(1 1 1) surface. This study maps electron transmission through the corral wall and provides
an extension of our earlier work focused on confinement in Cu corrals [S. Diaz-Tendero, F.E. Olsson, A.G.
28/02/2013
7
PUBLICATIONS
PROJETS 2008
Borisov, J.P. Gauyacq, Phys. Rev. B 77 (2008) 205403]. The existence of two decay modes for the confined
surface state is stressed: (i) non-resonant tunnelling through the corral wall concentrated on the Cu adatoms and
(ii) a resonant-induced decay involving the transient formation of a resonant state localized on top of the corral
wall. The present mapping of the electron transmission reveals how the interference between the two decay
modes works: there exist regions where the electron leaves the corral, balanced by regions where it enters the
corral, though the global behaviour of the quasi-stationary states is electron escape from the corral. (C) 2009
Elsevier B.V. All rights reserved.
[2008-005T] EXTREME
Porteur : Jean-Paul Itié
Axe A
A microscopic view on the Mott transition in chromium-doped V2O3
Auteurs : Lupi, S; Baldassarre, L; Mansart, B; Perucchi, A; Barinov, A; Dudin, P; Papalazarou, E;
Rodolakis, F; Rueff, JP; Itie, JP; Ravy, S; Nicoletti, D; Postorino, P; Hansmann, P; Parragh, N; Toschi, A;
Saha-Dasgupta, T; Andersen, OK; Sangiovanni, G; Held, K; Ma
Réf. : NATURE COMMUNICATIONS (2010) 105
V2O3 is the prototype system for the Mott transition, one of the most fundamental phenomena of electronic
correlation. Temperature, doping or pressure induce a metal-to-insulator transition (MIT) between a
paramagnetic metal (PM) and a paramagnetic insulator. This or related MITs have a high technological potential,
among others, for intelligent windows and field effect transistors. However the spatial scale on which such
transitions develop is not known in spite of their importance for research and applications. Here we unveil for the
first time the MIT in Cr-doped V2O3 with submicron lateral resolution: with decreasing temperature,
microscopic domains become metallic and coexist with an insulating background. This explains why the
associated PM phase is actually a poor metal. The phase separation can be associated with a thermodynamic
instability near the transition. This instability is reduced by pressure, that promotes a genuine Mott transition to
an eventually homogeneous metallic state.
28/02/2013
8
PUBLICATIONS
PROJETS 2008
[2008-007T] QCCM
Porteur : Olivier Dulieu
Axe B
Binary and ternary recombination of D-3(+) ions with electrons in
He-D-2 plasma
Auteurs : Glosik, J. Korolov, I Plasil, R. Kotrik, T. Dohnal, P. Novotny, O. Varju, J. Roucka, S. Greene,
CH. Kokoouline, V
Réf. : PHYSICAL REVIEW A 80 (2009) 042706
An experimental study is reported about the recombination of D-3(+) ions with electrons in a low-temperature
plasma (200-300K) consisting of He with a small admixture of D-2. At several temperatures, the pressure
dependence of the apparent binary recombination rate coefficient (alpha(eff)) was measured over a broad range
of helium pressures (200-2000 Pa). The binary and ternary recombination rate coefficients were obtained from
measured pressure dependences of alpha(eff). The binary recombination rate coefficient obtained alpha(bin)(300
K) = (2.7 +/- 0.9) x 10(-8) cm(3) s(-1) is in agreement with recent theory. The ternary recombination rate
coefficient obtained is K-He(300 K) = (1.8 +/- 0.6) x 10(-25) cm(6) s(-1). In analogy with the recently described
process of helium-assisted ternary recombination of H-3(+) ions, it is suggested that the ternary helium- assisted
recombination of D-3(+) ions proceeds through the formation of a neutral long- lived highly excited Rydberg
molecule D-3 followed by a collision with a He atom.
Binary and ternary recombination of H-3(+) and D-3(+) ions with
electrons in low temperature plasma
Auteurs : Glosik, J. Plasil, R. Kotrik, T. Dohnal, P. Varju, J. Hejduk, M. Korolov, I. Roucka, S.
Kokoouline, V
Réf. : MOLECULAR PHYSICS 108 (2010) 2253-2264
Measurements of recombination rate coefficients of binary and ternary recombination of H-3(+) and D-3(+) ions
with electrons in a low temperature plasma are described. The experiments were carried out in the afterglow
plasma in helium with a small admixture of Ar and parent gas (H-2 or D-2). For both ions a linear increase of
measured apparent binary recombination rate coefficients (alpha(eff)) with increasing helium density was
observed: alpha(eff) = alpha(BIN) + K-He[He]. From the measured dependencies, we have obtained for both
ions the binary (alpha(BIN)) and the ternary ( KHe) rate coefficients and their temperature dependence. For the
description of observed ternary recombination a mechanism with two subsequent rate determining steps is
proposed. In the first step, in H-3(+) + e(-) (or D-3(+) + e(-)) collision, a rotationally excited long-lived Rydberg
molecule H-3(*) (or D-3(*)) is formed. In the following step H-3(*) (or D-3(*)) collides with a He atom of the
buffer gas and this collision prevents autoionization of H-3(*) (or D-3(*)). Lifetimes of the formed H-3(*) (or D3(*)) and corresponding ternary recombination rate coefficients have been calculated. The theoretical and
measured binary and ternary recombination rate coefficients obtained for H-3(+) and D-3(+) ions are in good
agreement.
28/02/2013
9
PUBLICATIONS
PROJETS 2008
Calculation of rate constants for vibrational and rotational
excitation of the H+(3) ion by electron impact
Auteurs : Kokoouline, V.Faure, A. Tennyson, J. Greene, CH
Réf. : MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 405 (2010) 1195-1202
We present theoretical thermally averaged rate constants for vibrational and rotational (de-)excitation of the
H+(3) ion by electron impact. The constants are calculated using the multichannel quantum-defect approach. The
calculation includes processes that involve a change |delta J| < 2 in the rotational angular momentum J of H+(3).
The rate constants are calculated for states with J < 5 for rotational transitions of the H+(3) ground vibrational
level. The thermal rates for transitions among the lowest eight vibrational levels are also presented, averaged
over the rotational structure of the vibrational levels. The conditions for producing non-thermal rotational and
vibrational distributions of H+(3) in astrophysical environments are discussed.
Optical phase and the ionization-dissociation dynamics of excited
H2
Auteurs : A. Kirrander, H. H. Fielding, and Ch. Jungen
Réf. : J. Chem. Phys. 132, 024313 (2010)
Measurements of recombination rate coefficients of binary and ternary recombination of H-3(+) and D-3(+) ions
with electrons in a low temperature plasma are described. The experiments were carried out in the afterglow
plasma in helium with a small admixture of Ar and parent gas (H-2 or D-2). For both ions a linear increase of
measured apparent binary recombination rate coefficients (alpha(eff)) with increasing helium density was
observed: alpha(eff) = alpha(BIN) + K-He[He]. From the measured dependencies, we have obtained for both
ions the binary (alpha(BIN)) and the ternary ( KHe) rate coefficients and their temperature dependence. For the
description of observed ternary recombination a mechanism with two subsequent rate determining steps is
proposed. In the first step, in H-3(+) + e(-) (or D-3(+) + e(-)) collision, a rotationally excited long-lived Rydberg
molecule H-3(*) (or D-3(*)) is formed. In the following step H-3(*) (or D-3(*)) collides with a He atom of the
buffer gas and this collision prevents autoionization of H-3(*) (or D-3(*)). Lifetimes of the formed H-3(*) (or D3(*)) and corresponding ternary recombination rate coefficients have been calculated. The theoretical and
measured binary and ternary recombination rate coefficients obtained for H-3(+) and D-3(+) ions are in good
agreement.
Assignment of resonances in dissociative recombination of HD(+)
ions: High-resolution measurements compared with accurate
computations
Auteurs : Tamo, FOW; Buhr, H; Motapon, O; Altevogt, S; Andrianarijaona, VM; Grieser, M; Lammich, L;
Lestinsky, M; Motsch, M; Nevo, I; Novotny, S; Orlov, DA; Pedersen, HB; Schwalm, D; Sprenger, F;
Urbain, X; Weigel, U; Wolf, A; Schneider, IF
Réf. : PHYSICAL REVIEW A 84 (2): 10.1103/PhysRevA.84.022710 AUG 19 2011
The collision-energy resolved rate coefficient for dissociative recombination of HD(+) ions in the vibrational
ground state is measured using the photocathode electron target at the heavy-ion storage ring TSR. Rydberg
resonances associated with rovibrational excitation of the HD(+) core are scanned as a function of the electron
28/02/2013
10
PUBLICATIONS
PROJETS 2008
collision energy with an instrumental broadening below 1 meV in the low-energy limit. The measurement is
compared to calculations using multichannel quantum defect theory, accounting for rotational structure and
interactions and considering the six lowest rotational energy levels as initial ionic states. Using thermalequilibrium-level populations at 300 K to approximate the experimental conditions, close correspondence
between calculated and measured structures is found up to the first vibrational excitation threshold of the cations
near 0.24 eV. Detailed assignments, including naturally broadened and overlapping Rydberg resonances, are
performed for all structures up to 0.024 eV. Resonances from purely rotational excitation of the ion core are
found to have similar strengths as those involving vibrational excitation. A dominant low-energy resonance is
assigned to contributions from excited rotational states only. The results indicate strong modifications in the
energy dependence of the dissociative recombination rate coefficient through the rotational excitation of the
parent ions, and underline the need for studies with rotationally cold species to obtain results reflecting lowtemperature ionized media.
Electron collisions with BF+: bound and continuum states of BF
Auteurs : Chakrabarti K; Schneider, IF; Tennyson, J
Réf. : JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 44 (5) 055203 (2011)
Rydberg and continuum states of the BF molecule are studied as a function of geometry using an electron
collision formalism in the framework of the R-matrix method. Up to 14 BF+ target states are used in a closecoupling expansion and bound states are searched for as negative energy solutions of the scattering calculation.
Potential energy curves and quantum defects are obtained for the excited states of BF. Resonance positions and
widths are also calculated for Feshbach resonances in the system. The data obtained can be used to model
dissociative recombination of the BF+ molecular ion.
Formation of the simplest stable negative molecular ion H3- in
interstellar medium
Auteurs : M. Ayouz, R. Lopez, M. Raoult, J. Robert, O. Dulieu, V. Kokoouline
Réf. : Phys. Rev. A. 83, 052712 (2011)
We develop the theory of radiative association of an atom and a diatomic molecule within a close-coupling
framework. We apply it to the formation of H-3(-) after the low-energy collision (below 0.5 eV) of H-2 with H-.
Using recently obtained potential energy and permanent dipole moment surfaces of H-3(-), we calculate the
lowest rovibrational levels of the H-3(-) electronic ground state and the cross section for the formation of H-3(-)
by radiative association between H- and ortho- and para-H-2. We discuss the possibility for the H-3(-) ion to be
formed and observed in the cold and dense interstellar medium in an environment with a high ionization rate.
Such an observation could be a probe for the presence of H- in the interstellar medium.
Laser control of complete vibrational transfer in Na2 using
resonance coalescence
Auteurs : O. Atabek, R. Lefebvre, M. Lepers, A. Jaouadi, O. Dulieu, and V. Kokoouline
Réf. : Phys. Rev. Lett. 106, 173002 (2011)
Rydberg and continuum states of the BF molecule are studied as a function of geometry using an electron
collision formalism in the framework of the R-matrix method. Up to 14 BF+ target states are used in a closecoupling expansion and bound states are searched for as negative energy solutions of the scattering calculation.
28/02/2013
11
PUBLICATIONS
PROJETS 2008
Potential energy curves and quantum defects are obtained for the excited states of BF. Resonance positions and
widths are also calculated for Feshbach resonances in the system. The data obtained can be used to model
dissociative recombination of the BF+ molecular ion.
Laser cooling of the vibrational motion of Na(2) combining the
effects of zero-width resonances and exceptional points
Auteurs : R. Lefebvre, A. Jaouadi, O. Dulieu, O. Atabek
Réf. : PHYSICAL REVIEW A Volume: 84
Issue: 4
10.1103/PhysRevA.84.043428 Published: OCT 24 2011
Article Number: 043428
DOI:
We propose various scenarios for molecular vibrational cooling combining the effects of two kinds of resonance
states occurring during the photodissociation of Na(2) taken as an illustrative example. Such resonances result
from an appropriate sampling of laser parameters (wavelength and intensity): (a) For particular choices of
intensity and wavelength, two resonance energies can be brought to complete coalescence, with their positions
and widths becoming equal and leading to a so-called exceptional point (EP) in the parameter plane. Advantage
can be taken from such points for very selective laser-controlled vibrational transfer strategies. (b) For specific
intensities, far beyond the perturbation regime, some resonances can have a zero width (infinite lifetime). They
are referred to as a zero-width resonance (ZWR) and may be used for vibrational purification purposes. We show
how appropriately shaped, experimentally reachable laser pulses, encircling EPs or inducing ZWRs, may be used
for a thorough and comprehensive control aiming at population transfer or purification schemes, which, starting
from an initial field-free vibrational distribution, ends up in the ground vibrational level.
Photoassociation of a cold-atom-molecule pair. II. Second-order
perturbation approach
Auteurs : Lepers, M; Vexiau, R; Bouloufa, N; Olivier Dulieu; Kokoouline, V
The electrostatic interaction between an excited atom and a diatomic ground-state molecule in an arbitrary
rovibrational level at large mutual separations is investigated with a general second-order perturbation theory, in
the perspective of modeling the photoassociation between cold atoms and molecules. We find that the
combination of quadrupole-quadrupole and van der Waals interactions competes with the rotational energy of
the dimer, limiting the range of validity of the perturbative approach to distances larger than 100 Bohr radii.
Numerical results are given for the long-range interaction between Cs and Cs-2, showing that the
photoassociation is probably efficient for any Cs-2 rotational energy.
Proposal for a Laser Control of Vibrational Cooling in Na-2 Using
Resonance Coalescence
Auteurs : Atabek O, Lefebvre R, Lepers M, Jaouadi A, Olivier Dulieu, Kokoouline V
Réf. : PHYSICAL REVIEW LETTERS 106 (17): Art. No. 173002 APR 29 2011
With a specific choice of laser parameters resulting in a so-called exceptional point (EP) in the wavelengthintensity parameter plane, it is possible to produce the coalescence of two Floquet resonances describing the
photodissociation of the Na-2 molecule, which is one of the candidates for the formation of samples of
translationally cold molecules. By appropriately tuning laser parameters along a contour encircling the
28/02/2013
12
PUBLICATIONS
PROJETS 2008
exceptional point, the resonances exchange their quantum nature. Thus a laser-controlled transfer of the
probability density from one field-free vibrational level to another is achieved through adiabatic transport
involving these resonances. We propose an efficient scenario for vibrational cooling of Na-2 referring to cascade
transfers involving multiple EPs and predicted to be robust up to a 78% rate against laser-induced dissociation.
Triplet-singlet conversion in ultracold Cs-2 and production of
ground-state molecules
Auteurs : Bouloufa, N; Pichler, M; Aymar, M; Olivier Dulieu
Réf. : PHYSICAL REVIEW A
83 (2011) 022503
We propose a process to convert ultracold metastable Cs-2 molecules in their lowest triplet state into (singlet)
ground-state molecules in their lowest vibrational levels. Molecules are first pumped into an excited triplet state,
and the triplet-singlet conversion is facilitated by a two-step spontaneous decay through the coupled
A(1)Sigma(+)(u)-b(3)Pi(u) states. Using spectroscopic data and accurate quantum chemistry calculations for Cs2 potential curves and transition dipole moments, we show that this process competes favorably with the singlephoton decay back to the lowest triplet state. In addition, we demonstrate that this conversion process represents
a loss channel for vibrational cooling of metastable triplet molecules, preventing an efficient optical pumping
cycle down to low vibrational levels.
Breaking a tetrahedral molecular ion with electrons: study of NH4+
Auteurs : Douguet N.; Kokoouline V.; Orel A. E.
Réf. : JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Volume: 45 Issue: 5
Article Number: 051001 DOI: 10.1088/0953-4075/45/5/051001 Published: MAR 14 2012
We apply a general theoretical model to study the dissociative recombination of the polyatomic ion NH4+. The
high symmetry of the molecule, represented by the tetrahedral group, leads to complex vibronic couplings
responsible for dissociative recombination. By applying multi-channel quantum defect theory and using
symmetry considerations, we treat the doubly and triply degenerate modes and electronic states of NH4+ to
calculate a theoretical cross section. The cross section agrees well with existing experimental data.
Potential energy and dipole moment surfaces of HCO- for the
search of H- in the interstellar medium
Auteurs : Ayouz, M.; Mikhailov, I.; Babikov, D.; Raoult, M.; Galtier, S.; Dulieu, O.; Kokoouline, V.
Réf. : JOURNAL OF CHEMICAL PHYSICS Volume: 136
10.1063/1.4724096 Published: JUN 14 2012
Issue: 22
DOI:
Potential energy and permanent dipole moment surfaces of the electronic ground state of formyl negative ion
HCO- are determined for a large number of geometries using the coupled-cluster theory with single and double
and perturbative treatment of triple excitations ab initio method with a large basis set. The obtained data are used
to construct interpolated surfaces, which are extended analytically to the region of large separations between CO
and H- with the multipole expansion approach. We have calculated the energy of the lowest rovibrational levels
of HCO- that should guide the spectroscopic characterization of HCO- in laboratory experiments. The study can
also help to detect HCO- in the cold and dense regions of the interstellar medium where the anion could be
formed through the association of abundant CO with still unobserved H-. (C) 2012 American Institute of
Physics. [http://dx.doi.org/10.1063/1.4724096]
28/02/2013
13
PUBLICATIONS
PROJETS 2008
Photoassociation of a cold-atom-molecule pair: Long-range
quadrupole-quadrupole interactions
Auteurs : Lepers M, Olivier Dulieu, Kokoouline V
The general formalism of the multipolar expansion of electrostatic interactions is applied to the calculation of the
potential energy between an excited atom (without fine structure) and a ground-state diatomic molecule at large
mutual separations. Both partners exhibit a permanent quadrupole moment so that their mutual long-range
interaction is dominated by a quadrupole-quadrupole term, which is attractive enough to bind trimers. Numerical
results are given for an excited Cs(6(2)P) atom and a ground-state Cs-2 molecule. The prospects for achieving
photoassociation of a cold-atom-dimer pair are thus discussed and found promising. The formalism can be
generalized to the long-range interaction between molecules to investigate the formation of cold tetramers.
Cold atom-molecule photoassociation: long-range interactions
beyond the 1/Rn expansion
Auteurs : M. Lepers, O. Dulieu
Réf. : Eur. Phys. J. D 10.1140/epjd/e2011-20083-6 (2011)
We present a theoretical description of dissociative recombination of triatomic molecular ions having large
permanent dipole moments. The study has been partly motivated by a discrepancy between experimental and
theoretical cross sections for dissociative recombination of the HCO+ ion. The HCO+ ion has a considerable
permanent dipole moment (D approximate to 4 D), which has not been taken explicitly into account in previous
theoretical studies. In the present study, we include explicitly the effect of the permanent electric dipole on the
dynamics of the incident electron using the generalized quantum defect theory, and we present the resulting cross
section obtained. This demonstrates the possibility of applying generalized quantum defect theory to the
dissociative recombination of molecular ions.
Laser cooling of the vibrational motion of Na2 combining the
effects of Zero Width Resonances and Exceptional Points.
Auteurs : R. Lefebvre, A. Jouadi, O. Dulieu, O. Atabek
Réf. : Phys. Rev. A. in press 84 (2011) 043428
28/02/2013
14
PUBLICATIONS
PROJETS 2008
Long-range interactions between ultracold atoms and molecules
including atomic spin-orbit
Auteurs : M. Lepers, O. Dulieu
Réf. : Phys. Chem. Chem. Phys. In press
Photoassociation of a cold atom-molecule pair II: second-order
perturbation approach
Auteurs : M. Lepers, O. Dulieu, V. Kokoouline
Réf. : Phys Rev. A 83, 042707 (2011)
Potential energy and dipole moment surfaces of HCO- for the
search of H- in the interstellar medium
Auteurs : Ayouz M.; Mikhailov I.; Babikov D.; et al.
10.1063/1.4724096 Published: JUN 14 2012
Issue: 22 Article Number: 224310
DOI:
Potential energy and permanent dipole moment surfaces of the electronic ground state of formyl negative ion
HCO- are determined for a large number of geometries using the coupled-cluster theory with single and double
and perturbative treatment of triple excitations ab initio method with a large basis set. The obtained data are used
to construct interpolated surfaces, which are extended analytically to the region of large separations between CO
and H- with the multipole expansion approach. We have calculated the energy of the lowest rovibrational levels
of HCO- that should guide the spectroscopic characterization of HCO- in laboratory experiments. The study can
also help to detect HCO- in the cold and dense regions of the interstellar medium where the anion could be
formed through the association of abundant CO with still unobserved H-. (C) 2012 American Institute of
Physics. [http://dx.doi.org.gate4.inist.fr/10.1063/1.4724096]
28/02/2013
15
PUBLICATIONS
PROJETS 2008
Theory of dissociative recombination of a linear triatomic ion with
permanent electric dipole moment: Study of HCO+
Auteurs : Douguet, N. Kokoouline, V. Greene, CH
[2008-015T] ULYSSE & [2009-004T] ULYSSE II
Porteur : Yong Jin
Thème 1
Insight into low frequency noise induced by gate leakage current in
AlGaAs/GaAs high electron mobility transistors at 4.2 K
Auteurs : Liang, YX; Dong, Q; Cheng, MC; Gennser, U; Cavanna, A; Jin, Y
Réf. : APPLIED PHYSICS LETTERS 99 (11): 10.1063/1.3637054 SEP 12 2011
The bias-cooling method-the gate being kept biased at V(gc) during the cooling-has been used to investigate the
low frequency noise (LFN) in an AlGaAs/GaAs two-dimensional electron gas high electron mobility transistor at
4.2 K. For a chosen working point (i.e., a chosen drain bias/current), its gate bias V(gs), gate leakage current
I(gs), and LFN depend on V(gc). With the help of the heterostructure band diagram simulation for each V(gc),
the relation between I(gs) and the LFN can be elucidated by the gate Fermi level with regard to the
heterostructure band diagram. The LFN originated from I(gs) is caused by its sequential tunnelling component.
(C) 2011 American Institute of Physics. [doi:10.1063/1.3637054]
Input Noise Voltage Below 1 nV/Hz(1/2) at 1 kHz in the HEMTs at
4.2 K
Auteurs : Liang, Y. X.; Dong, Q.; Gennser, U.; Cavanna, A.; Jin, Y.
Réf. : JOURNAL OF LOW TEMPERATURE PHYSICS Volume: 167 Issue: 5-6 Pages: 632-637 DOI:
10.1007/s10909-012-0479-9 Part: Part 2 Published: JUN 2012
28/02/2013
16
PUBLICATIONS
PROJETS 2008
Specific High Electron Mobility Transistors (HEMTs) have been realized and characterized. At 4.2 K, with a
drain-source current I (ds) of 1.55 mA and drain-source voltage V (ds) of 100 mV, the transistor has the
following electrical characteristics: a transconductance and an output conductance of 69 and 3.8 mS,
respectively, leading to an intrinsic voltage gain of 18; an input gate-source capacitance C (gs) of about 31 pF;
and a gate leakage current less than 0.2 pA. An equivalent input noise voltage lower than 1 nV/Hz(1/2) at 1 kHz
has been achieved when I (ds)=1.55 mA at V (ds)=100 mV. Hence, our results show that the specific HEMTs
should be a suitable transistor for future ultra-low noise deep cryogenic low-frequency high-impedance readout
electronics.
The Role of the Gate Geometry for Cryogenic HEMTs: Towards an
Input Voltage Noise Below 0.5 nV/root Hz at 1 kHz and 4.2 K
Auteurs : Dong, Q.; Liang, Y. X.; Gennser, U.; Cavanna, A.; Jin, Y.
Réf. : JOURNAL OF LOW TEMPERATURE PHYSICS Volume: 167 Issue: 5-6 Pages: 626-631 DOI:
10.1007/s10909-012-0459-0 Part: Part 2 Published: JUN 2012
Specific HEMTs (High Electron Mobility Transistors) with different gate geometries have been realized on the
same AlGaAs/GaAs heterojunction. Under the same operating conditions with a power consumption of 30 mu w,
experimental results at 4.2 K and low frequency range show that the input voltage noise is almost inversely
proportional to the square root of the input capacitance: a noise value as low as 0.46 nV/v Hz at 1 kHz has been
obtained with an input capacitance of about 100 pF.
[2008-016T] SMGM
Porteur : Olivier Dauchot
Thème 3
Elementary excitation modes in a granular glass above jamming
Auteurs : Brito, C. Olivier Dauchot. Biroli, G. Bouchaud, JP
Réf. : SOFT MATTER 6 (2010) 3013-3022
The dynamics of granular media in the jammed, glassy region is described in terms of "modes'', by applying a
principal component analysis (PCA) to the covariance matrix of the position of individual grains. We first
demonstrate that this description is justified and gives sensible results in a regime of time/densities such that a
metastable state can be observed on a long enough timescale to define the reference configuration. For small
enough times/system sizes, or at high enough packing fractions, the spectral properties of the covariance matrix
reveals large, collective fluctuation modes that cannot be explained by a random matrix benchmark where these
correlations are discarded. We then present a first attempt to find a link between the softest modes of the
covariance matrix during a certain "quiet'' time interval and the spatial structure of the rearrangement event that
ends this quiet period. The motion during these cracks is indeed well explained by the soft modes of the
dynamics before the crack, but the number of cracks preceded by a "quiet'' period strongly reduces when the
system unjams, questioning the relevance of a description in terms of modes close to the jamming transition, at
least for frictional grains.
28/02/2013
17
PUBLICATIONS
PROJETS 2008
[2008-019T] MCQM
Porteur : Rosa Tualle-Brouri
Thème 1
Multiple-measurement Leggett-Garg inequalities
Auteurs : Barbieri, M
In the investigation of the quantum to classical transition, the Leggett-Garg inequality represents what Bell's
inequality is for the study of entanglement and nonlocality: a definite quantitative test showing the inadequacy of
familiar lines of thought in interpreting quantum phenomena. Here we discuss the generalization of the LeggettGarg inequality to an arbitrary number of measurements in the perspective of its use as a tool for characterizing
nondestructive measurement devices.
Implementation of a Nondeterministic Optical Noiseless Amplifier
Auteurs : Ferreyrol, F. Barbieri, M. Blandino, R. Fossier, S. Rosa Tualle-Brouri.Grangier, P
Quantum mechanics imposes that any amplifier that works independently on the phase of the input signal has to
introduce some excess noise. The impossibility of such a noiseless amplifier is rooted in the unitarity and
linearity of quantum evolution. A possible way to circumvent this limitation is to interrupt such evolution via a
measurement, providing a random outcome able to herald a successful-and noiseless-amplification event. Here
we show a successful realization of such an approach; we perform a full characterization of an amplified
coherent state using quantum homodyne tomography, and observe a strong heralded amplification, with about a
6 dB gain and a noise level significantly smaller than the minimal allowed for any ordinary phase-independent
device.
Nondeterministic noiseless amplification of optical signals: a
review of recent experiments
Auteurs : Barbieri, M, Ferreyrol, F, Blandino, R, Rosa Tualle-Brouri, Grangier, P
Réf. : LASER PHYSICS LETTERS 8 (6): 411-417 JUN 2011
Linear amplifiers necessarily introduce a minimal amount of noise, as required by Heisenberg's relation in
quantum mechanics. Such a limitation could be overcome when considering nondeterminsitic processes,
heralded by a trigger event. Here we present a review of implementations of this technique, which have recently
appeared in the literature.
28/02/2013
18
PUBLICATIONS
PROJETS 2008
[2008-020T] MICROHALL
Porteur : Denis L'Hôte
Axe A
A local noise measurement device for magnetic physical systems
Auteurs : L'Hote D, Nakamae S, Ladieu F, Mosser V, Kerlain A, Konczykowski M
Réf. : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT (2009) P01027
We present an experimental setup developed to measure locally the fluctuations of the magnetization of physical
systems such as spin and superspin glasses. It is based on micronic and submicronic Hall probes. We present the
noise reduction at ambient temperature owing to the use of the spinning current technique. Finally, we show
why, with such probes, the noise measured on a macroscopic sample probes only a microscopic volume of the
sample.
[2008-025T] FLUCT-DMABN
Porteur : Thomas Gustavsson
Thème 2
Do fluorescence and transient absorption probe the same
intramolecular charge transfer state of 4(dimethylamino)benzonitrile?
Auteurs : Gustavsson, T. Coto, PB. Serrano-Andres, L. Fujiwara, T. Lim, EC
Réf. : JOURNAL OF CHEMICAL PHYSICS
131 (2009) 031101
We present here the results of time-resolved absorption and emission experiments for 4(dimethylamino)benzonitrile in solution, which suggest that the fluorescent intramolecular charge transfer (ICT)
state may differ from the twisted ICT (TICT) state observed in transient absorption.
Intramolecular charge transfer and dual fluorescence of 4(dimethylamino) benzonitrile: ultrafast branching followed by a
two-fold decay mechanism
Auteurs : Coto, Pedro B.; Serrano-Andres, Luis; Gustavsson, Thomas; Fujiwara, Takashige; Lim,
Edward C.
Réf. : PHYSICAL CHEMISTRY CHEMICAL PHYSICS 13 (33): 15182-15188 10.1039/c1cp21089k 2011
28/02/2013
19
PUBLICATIONS
PROJETS 2008
In this contribution we present new experimental and theoretical results for the intramolecular charge transfer
(ICT) reaction underlying the dual fluorescence of 4-(dimethylamino) benzonitrile ( DMABN), which indicate
that the fully twisted ICT (TICT) state is responsible for the time-resolved transient absorption spectrum while a
distinct partially twisted ICT (pTICT) structure is suggested for the fluorescent ICT state.
[2008-026T] Prodymag
Porteur : J. Ferré/A. Thiaville
Axe B
Dynamic fluctuations and two-dimensional melting at the spin
reorientation transition
Auteurs : Bergeard, N. (1,2); Jamet, JP (1); Mougin, A (1); Ferre, J (1); Gierak, J (3); Bourhis, E (3);
Stamps, R (4)
Réf. : PHYSICAL REVIEW B Volume: 86
Issue: 9
10.1103/PhysRevB.86.094431 Published: SEP 25 2012
DOI:
Instabilities and strong spatiotemporal fluctuations in out-of-plane demagnetized stripe domain patterns of a
Pt/Co(0.5 nm)/Pt film designed by Ga+ ion irradiation were visualized by polar magneto-optical Kerr effect
microscopy and studied in the spin reorientation transition temperature region. A two-dimensional-stripe melting
transition was evidenced before reaching the in-plane spin state. Slow dynamics were driven by short-range
instabilities on magnetic defects which trigger long-range transverse wall fluctuations. The spatial and temporal
behavior of stripelike "floating" patches was investigated. Dynamics cannot be simply interpreted by models
previously proposed for liquid crystals.
[2008-027T] POMICO
Porteur : Jean Daillant
Axe B
Organization of Block Copolymers using NanoImprint Lithography:
Comparison of Theory and Experiments
Auteurs : Man, XK; Andelman, D; Orland, H; Thebault, P; Liu, PH; Guenoun, P; Jean Daillant; Landis, S
Réf. : MACROMOLECULES 44 (2011) 2206-2211
We present NanoImprint lithography experiments and modeling of thin films of block copolymers (BCP). The
NanoImprint technique is found to be an efficient tool not only to align lamellar phases perpendicularly to the
28/02/2013
20
PUBLICATIONS
PROJETS 2008
substrate but also to get rid of in-plane defects over distances much larger than the natural lamellar periodicity.
The modeling relies on self-consistent field calculations done in two- and three-dimensions and is found to be in
good agreement with the experiments. It also offers some insight on the Nanolmprint lithography setup and on
the conditions required to perfectly ordered BCP lamellae.
Tailoring Nanostructures Using Copolymer Nanoimprint
Lithography
Auteurs : Thebault Pascal; Niedermayer Stefan; Landis Stefan; et al.
Réf. : ADVANCED MATERIALS
Volume: 24
10.1002/adma.201103532 Published: APR 17 2012
Issue: 15
Pages: 1952-1955
DOI:
Pas d'abstract
Block Copolymer at Nano-Patterned Surfaces
Auteurs : Man XK, Andelman D, Orland H
Réf. : MACROMOLECULES 43 (2010)
We present numerical calculations of lamellar phases of block copolymers at patterned surfaces. We model
symmetric diblock copolymer films forming lamellar phases and the effect of geometrical and chemical surface
patterning on the alignment and orientation of lamellar phases. The calculations are done within self-consistent
field theory (SCFT), where the semi-implicit relaxation scheme is used to solve the diffusion equation. Two
specific setups, motivated by recent experiments, are investigated. In the first, the film is placed on top of a
surface imprinted with long chemical stripes. The stripes interact more favorably with one of the two blocks and
induce a perpendicular orientation in a large range of system parameters. However, the system is found to be
sensitive to its initial conditions and sometimes gets trapped into a metastable mixed state composed of domains
in parallel and perpendicular orientations. In a second setup, we study the film structure and orientation when it
is pressed against a hard grooved mold. The mold surface prefers one of the two components, and this setup is
found to be superior for inducing a perfect perpendicular lamellar orientation for a wide range of system
parameters.
[2008-028T] MASLOV
Porteur : Montambaux, G
Thème 4
Nonanalytic Spin Susceptibility of a Fermi Liquid: The Case of FeBased Pnictides
Auteurs : Korshunov, MM. Eremin, I. Efremov, DV. Maslov, DL. Chubukov, AV
28/02/2013
21
PUBLICATIONS
PROJETS 2008
We propose an explanation of the peculiar linear temperature dependence of the uniform spin susceptibility
chi(T) in ferropnictides. We argue that the linear in T term appears to be due to the nonanalytic temperature
dependence of chi(T) in a two-dimensional Fermi liquid. We show that the prefactor of the T term is expressed
via the square of the spin-density-wave (SDW) amplitude connecting nested hole and electron pockets. Because
of an incipient SDW instability, this amplitude is large, which, along with a small value of the Fermi energy,
makes the T dependence of chi(T) strong. We demonstrate that this mechanism is in quantitative agreement with
the experiment.
[2008-029T] HY-IRGS-2
Porteur : Eric Vincent
Axe B
Emergence of Rigidity at the Structural Glass Transition: A FirstPrinciples Computation
Auteurs : Yoshino, H. Mezard, M
We compute the shear modulus of structural glasses from a first-principles approach based on the cloned liquid
theory. We find that the intrastate shear modulus, which corresponds to the plateau modulus measured in linear
viscoelastic measurements, strongly depends on temperature and vanishes continuously when the temperature is
increased beyond the glass temperature.
Replica theory of the rigidity of structural glasses
Auteurs : Yoshino, Hajime
10.1063/1.4722343 Published: JUN 7 2012
Issue: 21
DOI:
We present a first principle scheme to compute the rigidity, i.e., the shear-modulus of structural glasses at finite
temperatures using the cloned liquid theory, which combines the replica theory and the liquid theory. With the
aid of the replica method which enables disentanglement of thermal fluctuations in liquids into intra-state and
inter-state fluctuations, we extract the rigidity of metastable amorphous solid states in the supercooled liquid and
glass phases. The result can be understood intuitively without replicas. As a test case, we apply the scheme to the
supercooled and glassy state of a binary mixture of soft-spheres. The result compares well with the shearmodulus obtained by a previous molecular dynamic simulation. The rigidity of metastable states is significantly
reduced with respect to the instantaneous rigidity, namely, the Born term, due to non-affine responses caused by
displacements of particles inside cages at all temperatures down to T = 0. It becomes nearly independent of
temperature below the Kauzmann temperature T-K. At higher temperatures in the supercooled liquid state, the
non-affine correction to the rigidity becomes stronger suggesting melting of the metastable solid state. Inter-state
part of the static response implies jerky, intermittent stress-strain curves with static analogue of yielding at
mesoscopic scales. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4722343]
28/02/2013
22
PUBLICATIONS
PROJETS 2008
[2008-031T] STOLTE
Porteur : Benoît Soep
Thème 2
Unusual Quantum Interference in the S-1 State of DABCO and
Observation of Intramolecular Vibrational Redistribution
Auteurs : Poisson, L. Maksimenska, R. Soep, B. Jean-Michel Mestdagh. Parker, DH. Nsangou,
M.Hochlaf, M
Réf. : JOURNAL OF PHYSICAL CHEMISTRY A 114 (2010) 11269-11276
In this paper we report an experimental study of the time-resolved response of the molecule 1,4diazabicyclo[2.2.2]octane (DABCO) to 266.3 nm electronic excitation of the S-1 state with a femtosecond laser.
Rotational decoherence and vibrational oscillation within the S-1 state are observed. We performed state-of-theart ab initio calculations on the ground and low electronic states of the neutral molecule and the cation, which
assist in the assignment of the observed photoelectron signals. Using our theoretical and spectroscopic data, the
experimental findings are interpreted in terms of an unusual quantum interference between two different
vibrational modes, with only the v = 1 level of each mode being populated.
[2008-032T] B-DIAMANT
Porteur : Jean-François Roch
Thème 7
Influence of a static magnetic field on the photoluminescence of an
ensemble of nitrogen-vacancy color centers in a diamond singlecrystal
Auteurs : Lai ND, Zheng DW, Jelezko F, Treussart F, Roch JF
Réf. : APPLIED PHYSICS LETTERS 95 (2009) 133101
We investigate the electron spin resonance of an ensemble of nitrogen-vacancy (NV) color centers in a bulk
diamond crystal. The four possible orientations of the NV center in the lattice lead to different dependences on
the magnitude and the orientation of an external static magnetic field. Experimental results obtained with a
continuous microwave excitation are in good agreement with simulations. In addition, we observe that the
average radiative lifetime of the NV color center is also modified when the external magnetic field is applied.
This variation is explained by the mixing between m(S)=0 and m(S)=+/- 1 spin states of the NV center with
different radiative lifetimes, due to magnetic coupling. These results are of interest for a broad range of
applications, such as spin-resonance-based magnetometry with a high-density ensemble of NV centers. (C) 2009
American Institute of Physics.
28/02/2013
23
PUBLICATIONS
PROJETS 2008
Avoiding power broadening in optically detected magnetic
resonance of single NV defects for enhanced dc magnetic field
sensitivity
Auteurs : A Dreau, M Lesik, L Rondin, P Spinicelli, O Arcizet, JF Roch, V Jacques
Réf. : PHYSICAL REVIEW B, 84 (19):10.1103/PhysRevB.84.195204 NOV 23 2011
We report a systematic study of the magnetic field sensitivity of a magnetic sensor consisting of a single
nitrogen-vacancy (NV) defect in diamond, by using continuous optically detected electron spin resonance (ESR)
spectroscopy. We first investigate the behavior of the ESR contrast and linewidth as a function of the microwave
and optical pumping power. The experimental results are in good agreement with a simplified model of the NV
defect spin dynamics, leading to an optimized sensitivity around 2 mu T/root Hz for a single NV defect in a
high-purity diamond crystal grown by chemical vapor deposition. We then demonstrate an enhancement of the
magnetic sensitivity by one order of magnitude by using a simple pulsed-ESR scheme. This technique is based
on repetitive excitation of the NV defect with a resonant microwave pi pulse followed by an optimized readout
laser pulse, allowing to fully eliminate power broadening of the ESR linewidth. The achieved sensitivity is
similar to that obtained by using Ramsey-type sequences, which is the optimal magnetic field sensitivity for the
detection of a dc magnetic field.
[2008-046T] DYNELEC
Porteur : Danielle Dowek
Thème 2
Ion Pair Formation in Multiphoton Excitation of NO2 Using Linearly
and Circularly Polarized Femtosecond Light Pulses: Kinetic Energy
Distribution and Fragment Recoil Anisotropy
Auteurs : Elkharrat, C. Picard, YJ. Billaud, P. Cornaggia, C. Garzella, D. Perdrix, M. Houver, JC.
Lucchese, RR. Dowek, D
Réf. : JOURNAL OF PHYSICAL CHEMISTRY A 114 (2010) 9902-9918
The NO2 ion pair photodissociation dynamics leading to NO+ (X-1 Sigma(+), v) + O-(P-2(3/2) or P-2(1/2)),
induced by a 1 kHz fermtosecond laser with wavelengths near 400 nm, has been characterized using the
coincidence vector correlation method. The ion pair production after four-photon absorption reaches more than
15% of the primary ionization. The kinetic energy release of the fragments demonstrates a significant vibrational
excitation of the NO+ (X-1 Sigma(+), v) molecular fragment. Recoil ion fragment emission is strongly aligned
along the polarization axis of linearly polarized light or preferentially emitted in the plane perpendicular to the
propagation axis of circularly polarized light. The formalism describing the recoil anisotropy for bound-to-bound
n-photon transition inducing prompt axial recoil dissociation of a nonlinear molecule has been developed to
interpret the measured anisotropies in terms of excitation pathways via near-resonant intermediate states of
specific symmetries. Possible reaction pathways are discussed that are consistent with the data and supported by
calculations of potential energy surfaces and transition moments.
28/02/2013
24
PUBLICATIONS
PROJETS 2008
Molecular frame photoemission in dissociative ionization of H-2 and
D-2 induced by high harmonic generation femtosecond XUV pulses
Auteurs : Billaud, P. (1,2); Geleoc, M. (3); Picard, YJ (1,2); Veyrinas, K (1,2); Hergott, JF (3); Poullain,
SM (1,2); Breger, P (3); Ruchon, T (3); Roulliay, M (1,2); Delmotte, F (4); Lepetit, F (3); Huetz, A (1,2);
Carre, B (3); Dowek, D (1,2)
Réf. : JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Volume: 45 Issue: 19
Special Issue: SI Article Number: 194013 DOI: 10.1088/0953-4075/45/19/194013 Published: OCT
14 2012
We report the first results of molecular frame photoelectron emission for dissociative photoionization (DPI) of
H-2 and D-2 molecules induced by a spectrally filtered single high harmonic of a few femtosecond duration,
using coincident electron-ion velocity vector correlation techniques. For the studied photon energies around 32
eV, where the resonant excitation of the Q(1) and Q(2) doubly excited states occurs, autoionization and nuclear
dynamics are coupled on a few femtosecond timescale, giving rise to quantum interferences. Molecular frame
photoelectron angular distributions (MFPADs), traced as a function of the kinetic energy release of the atomic
fragments, provide the most sensitive observables for such complex dynamics. These results compare well with
recent spectrally resolved experiments using synchrotron radiation which are also reported. As a novel XUV
light source running at multi-kHz repetition rate and synchronized with laser pulses, high-order harmonic
generation (HHG) opens new possibilities for extending these investigations to time-resolved studies at the
femtosecond scale.
[2008-047T] GAIN
Porteur : Moustapha El Kurdi
Thème 7
Enhanced photoluminescence of heavily n-doped germanium
Auteurs : Moustapha El Kurdi. Kociniewski, T. Ngo, TP. Boulmer, J. Debarre, D. Boucaud, P.
Damlencourt, JF. Kermarrec, O. Bensahel, D
We show that a significant enhancement of the direct band gap photoluminescence can be achieved at room
temperature in bulk Ge and Ge-on-insulator heavily n-doped by gas immersion laser doping. The
photoluminescence signal from bulk Ge and Ge-on-insulator increases with the donor concentration. An
enhancement factor of 20 as compared to the undoped material is achieved near the 1550 nm wavelength for
active dopant concentrations around 5x10(19) cm(-3). These results are supported by calculations of the Ge
spontaneous emission spectrum taking into account the doping effect on the electron distribution in the direct
and indirect conduction band valleys.
28/02/2013
25
PUBLICATIONS
PROJETS 2008
Band structure and optical gain of tensile-strained germanium
based on a 30 band k center dot p formalism
Auteurs : Moustapha El Kurdi. Fishman, G. Sauvage, S. Boucaud, P
Réf. : JOURNAL OF APPLIED PHYSICS 107 (2010) 013710
We have investigated the band structure of tensile-strained germanium using a 30 band k center dot p formalism.
This multiband formalism allows to simultaneously describe the valence and conduction bands, including the L,
Delta, and Gamma valleys. We calculate the energy band variation as a function of strain and obtain that the
crossover from indirect to direct band gap occurs for a tensile in-plane strain of 1.9%. The effective masses of
density of states are deduced from the calculated conduction and valence band density of states. Significant
deviations are observed as compared to the effective masses of density of states values of unstrained bulk
germanium. We finally calculate the optical gain that can be achieved with tensile-strained bulk germanium. An
optical gain larger than 3000 cm(-1) is predicted for a carrier density of 1x10(18) cm(-3) and a 3% in-plane
biaxial strain. This optical gain is larger than the one of GaAs calculated with the same formalism and is much
larger than the experimental free-carrier absorption losses. This gain should be sufficient to achieve lasing in
these structures.
Control of direct band gap emission of bulk germanium by
mechanical tensile strain
Auteurs : Kurdi, M. Bertin, H. Martincic, E. de Kersauson, M. Fishman, G. Sauvage, S. Bosseboeuf, A.
Boucaud, P
We show that the recombination energy of the direct band gap photoluminescence (PL) of germanium can be
controlled by an external mechanical stress. The stress is provided by an apparatus commonly used for bulge or
blister test. An energy redshift up to 60 meV is demonstrated for the room temperature PL of a thin germanium
membrane (125 nm wavelength shift from 1535 to 1660 nm). This PL shift is correlated with the in-plane tensile
strain generated in the film. A biaxial tensile strain larger than 0.6% is achieved by this method. This mechanical
strain allows to approach the direct band gap condition for germanium which is of tremendous importance to
achieve lasing with this material.
Direct and indirect band gap room temperature
electroluminescence of Ge diodes
Auteurs : de Kersauson, M. Jakomin, R. Moustapha El Kurdi. Beaudoin, G. Zerounian, N. Aniel, F.
Sauvage, S. Sagnes, I.Boucaud, P
Réf. : JOURNAL OF APPLIED PHYSICS 108 (2010) 023105
Germanium is a promising material for electrically pumped light emitters integrated on silicon. In this work, we
have investigated the room temperature electroluminescence of pure germanium diodes grown by metal organic
chemical vapor deposition. The dependence of the optical response of the p-n diodes is studied as a function of
the injected current. Both direct and indirect band gap recombinations are observed at room temperature around
1.6 and 1.8 mu m. The amplitude of the direct band gap recombination is equivalent to the one of the indirect
band gap. (C) 2010 American Institute of Physics. [doi:10.1063/1.3462400]
28/02/2013
26
PUBLICATIONS
PROJETS 2008
Control of tensile strain in germanium waveguides through silicon
nitride layers
Auteurs : Ghrib A.; de Kersauson M.; El Kurdi M.; et al.
Réf. : APPLIED PHYSICS LETTERS Volume: 100
10.1063/1.4718525 Published: MAY 14 2012
Issue: 20
DOI:
Germanium ridge waveguides can be tensilely strained using silicon nitride thin films as stressors. We show that
the strain transfer in germanium depends on the width of the waveguides. Carrier population in the zone center
Gamma valley can also be significantly increased when the ridges are oriented along the < 100 > direction. We
demonstrate an uniaxial strain transfer up to 1% observed on the room temperature direct band gap
photoluminescence of germanium. The results are supported by 30 band k . p modeling of the electronic
structure and the finite element modeling of the strain field. (C) 2012 American Institute of Physics.
[http://dx.doi.org.gate4.inist.fr/10.1063/1.4718525]
[2008-048T] SPECTMAG
Porteur : Jean-Christophe Girard
Axe A
Atomic structure of tip apex for spin-polarized scanning tunneling
microscopy
Auteurs : Rodary, G; Jean-Christophe Girard
ean-ChristopheGirard ; Largeau, L; David, C; Mauguin, O; Wang, ZZ
Réf. : APPLIED PHYSICS LETTERS 98 (2011)
082505
We present a high resolution transmission electron microscopy study of a Cr-coated W tip apex prepared for
spin-polarized scanning tunneling microscopy (SP-STM). The characterization of the tip apex structure has been
done with atomic resolution. We show that the Cr film is epitaxially grown on W and presents a monocrystalline
phase. The surface analysis of the apex reveals roughness which gives rise to structures that can be considered as
nanotips. In spite of the monocrystalline structure of these nanotips, we show that their spin arrangement and
resulting magnetization direction cannot be controlled. SP-STM measurements on a Cr/MgO(001) sample
confirm this conclusion. (C) 2011 American Institute of Physics.
28/02/2013
27
PUBLICATIONS
PROJETS 2008
[2008-051T] PHOTO-MAG
Porteur : Isabelle Maurin
Axe C
Controlled growth of core@shell heterostructures based on
Prussian blue analogues
Auteurs : Presle, M; Lemainque, J; Guigner, JM; Larquet, E; Isabelle Maurin; Boilot, JP; Gacoin, T
Réf. : NEW JOURNAL OF CHEMISTRY 35 (6): 1296-1301 2011
This work aims to develop a controlled strategy for the growth of multifunctional core@shell nanoparticles
based on Prussian blue analogues. We mainly focussed our attention on Rb0.45Co[Fe(CN)(6)](0.8)center dot
3H(2)[email protected][Cr(CN)(6)](0.7)center dot zH(2)O particles, which combine a photoswitchable (photomagnetic/-chromic) core with a ferromagnetic shell. The control of the chemical composition in the
heterostructure is a key point to obtain the expected magnetic, optical and structural properties. We found that
the removal of the unreacted species by washing after the growth of the primary particles led to an irreversible
aggregation attributed to the desorption of stabilizing [Fe(CN)(6)]surface units. We showed that this difficulty
could be overcome by washing the particles in a solution containing chromicyanide ions, which are precursors of
the Rb0.2Ni[Cr(CN)(6)](0.7)center dot zH(2)O shell phase, thus avoiding a contamination of the shell. Both Xray diffraction and magnetic measurements confirmed that a controlled shell of the desired composition could
be obtained this way.
Magnetic Core-Shell Nanoparticles from Nanoscale-Induced Phase
Segregation
Auteurs : Carenco Sophie; Le Goff Xavier F.; Shi Jing; et al.
Réf. : CHEMISTRY OF MATERIALS
Volume: 23
10.1021/cm200575g Published: APR 26 2011
Issue: 8
Pages: 2270-2277
DOI:
Nanoscaling of the nickel phosphides profoundly alters their domains of stability. An original mechanism of
"nanoscale-induced phase segregation" was uncovered in the present study: the appearance of two crystallized
phases inside each single nanoparticle (here, Ni(2)P and Ni fcc), where the single-phase product (Ni(3)P) would
have been preferred at the bulk scale. This behavior was obtained by reacting at low temperature (<220 degrees
C) substoichiometric amounts of white phosphorus (P(4)) on well-defined monodisperse Ni nanoparticles in
solution. Phosphorus insertion inside the Ni fcc nanoparticles triggers the crystallization of a Ni(2)P core
surrounded by a Ni shell. The crystallization process was monitored by HRTEM, EFTEM, XRD, and SQUID
analyses and revealed a direct transformation of Ni fcc to a core-shell structure without any other Ni(x)P(y)
crystallized intermediate. This core-shell Ni-P system was tuned by adjusting the amount of P(4) added,
providing tunable magnetic shells supported on monodisperse nanoparticles.
28/02/2013
28
PUBLICATIONS
PROJETS 2008
Influence of Protected Annealing on the Magnetic Properties of
gamma-Fe2O3 Nanoparticles
Auteurs : Vichery, Charlotte; Maurin, Isabelle; Bonville, Pierre; Boilot, Jean-Pierre; Gacoin, Thierry
Réf. : JOURNAL OF PHYSICAL CHEMISTRY C Volume: 116
10.1021/jp305069a Published: AUG 2 2012
Issue: 30
Pages: 16311-16318
DOI:
It is usually considered that nanoparticles synthesized by low-temperature routes present structural disorder,
from extended defects to local rearrangements (e.g., vacancy ordering or inversion in spinel ferrites), that may
severely impact their magnetic properties. In the present work, we have investigated the influence of
postsynthesis thermal treatments on 7-nm-sized gamma-Fe2O3 nanoparticles prepared by room temperature
coprecipitation of ferric and ferrous salts in alkaline medium, followed by the dispersion of the preformed
particles in a sol gel silica binder. Such protected annealing in a refractory matrix prevents coalescence and
growth, thus preserving the mean size and size distribution of the pristine particles. Structural characterizations
show that heat treatments up to 1000 degrees C turned the raw grains into well-crystallized particles without
transformation into hematite. This strategy thus allows accounting for the influence of structural rearrangements
on magnetic properties at fixed particle size. For such 7 nm particles, postsynthesis heat treatments were found to
the shell of misaligned spins at the surface.
[2008-052T] ACOUSTIC
Porteur : Sébastien Sauvage
Thème 7
Homogeneous broadening of the S to P transition in InGaAs/GaAs
quantum dots measured by infrared absorption imaging with
nanoscale resolution
Auteurs : Sauvage S, Driss A, Reveret F; Boucaud, P Dazzi, A Prazeres, R Glotin, F Jean-Michel Ortega,
JM Miard, A Halioua, Y Raineri, F Sagnes, I Lemaitre, A
Absorption of single InGaAs self-assembled quantum dots is spatially resolved in resonance with the S to P
polaron transitions around lambda = 25 mu m wavelength. We show that the spatial resolution down to 50 nm
(lambda/500) combined with the analysis of the absorption nanoscopy images provides a measurement of the
homogeneous broadening at room temperature. The 2.5 +/- 1 meV measured S-P homogeneous broadening
supports the calculated value accounting for acoustic phonon-induced decoherence.
28/02/2013
29
PUBLICATIONS
PROJETS 2008
[2008-053T] SERPBIO
Porteur : Niloufar Shafizadeh
Thème 2
First observation in the gas phase of the ultrafast electronic
relaxation pathways of the S-2 states of heme and hemin
Auteurs : Ha-Thi MH ; Niloufar Shafizadeh ; Poisson L ; Soep B
Réf. : PHYSICAL CHEMISTRY CHEMICAL PHYSICS 12 (2010) 14985-14993
The time evolution of electronically excited heme (iron II protoporphyrin IX, [Fe-II PP]) and its associated salt
hemin (iron III protoporphyrin IX chloride, [Fe-III PP-Cl]), has been investigated for the first time in the gas
phase by femtosecond pump-probe spectroscopy. The porphyrins were excited at 400 nm in the S-2 state (Soret
band) and their relaxation dynamics was probed by multiphoton ionization at 800 nm. This time evolution was
compared with that of the excited state of zinc protoporphyrin IX [Zn PP] whose S2 excited state likely decays to
the long lived S-1 state through a conical intersection, in less than 100 fs. Instead, for [Fe-II PP] and [Fe-III PPCl], the key relaxation step from S-2 is interpreted as an ultrafast charge transfer from the porphyrin excited
orbital pi* to a vacant d orbital on the iron atom (ligand to metal charge transfer, LMCT). This intermediate
LMCT state then relaxes to the ground state within 250 fs. Through this work a new, serendipitous, preparation
step was found for Fe II porphyrins, in the gas phase.
Strength of (NHS)-S-Hydrogen Bonds in Methionine Residues
Revealed by Gas-Phase IR/UV Spectroscopy
Auteurs : Biswal Himansu S.; Gloaguen Eric; Loquais Yohan; et al.
Réf. : JOURNAL OF PHYSICAL CHEMISTRY LETTERS Volume: 3
10.1021/jz300207k Published: MAR 15 2012
Issue: 6
Pages: 755-759
DOI:
Despite of being ubiquitous in proteins, (NHbackboneS)-S-... hydrogen bonds linking the sulfur atom of
methionine or cysteine to backbone NH groups remain poorly documented. Here, we report vibrationally
resolved IR NH stretch spectra of two methionine-containing dipeptides (Ac-Phe-Met-NH2 and Ac-Met-PheNH2). The conformations observed for both molecules, assigned with the help of DFT-D quantum chemistry,
provide spectroscopic evidence for the formation of (NHbackboneS)-S-... H-bonds, surprisingly strong enough
to challenge the classical intrabackbone (NHO)-O-...=C H-bonds. The methionine side chain is found to fold
locally, forming a H-bond with the neighboring amide groups (NH(i) or NH(i+1)). Comparison with protein data
bank structural information shows that such a local folding is also common in proteins where it concerns 24% of
the methionine residues that have a sulfur atom linked to a backbone NH group. This convergence between the
strength of these (NHS)-S-... H-bonds and protein structural data illustrates their contribution to the stability of
protein chains.
28/02/2013
30
PUBLICATIONS
PROJETS 2008
[2008-053T] SERPEBIO & [2010-003T] COMOVA
Porteur : Niloufar Shafizadeh
Thème 2
Unraveling the Mechanisms of Nonradiative Deactivation in Model
Peptides Following Photoexcitation of a Phenylalanine Residue
Auteurs : Malis, Momir; Loquais, Yohan; Gloaguen, Eric; Biswal, Himansu S.; Piuzzi, Francois; Tardivel,
Benjamin; Brenner, Valerie; Broquier, Michel; Jouvet, Christophe; Mons, Michel; Doslic, Nada; Ljubic,
Ivan
Réf. : JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Volume: 134
20351 DOI: 10.1021/ja3054942 Published: DEC 19 2012
Issue: 50
Pages: 20340-
The mechanisms of nonradiative deactivation of a phenylalanine residue after near-UV photoexcitation have
been investigated in an isolated peptide chain model (N-acetylphenylalaninylamide, NAPA) both experimentally
and theoretically. Lifetime measurements at the origin of the first pi pi* state of jet-cooled NAPA molecules
have shown that (i) among the three most stable conformers of the molecule, the folded conformer NAPA B is
similar to 50-times shorter lived than the extended major conformer NAPA A and (ii) this lifetime is virtually
insensitive to deuteration at the NH2 and NH sites. Concurrent time-dependent density functional theory
(TDDFT) based nonadiabatic dynamics simulations in the full dimensionality, carried out for the NAPA B
conformer, provided direct insights on novel classes of ultrafast deactivation mechanisms, proceeding through
several conical intersections and leading in fine to the ground state. These mechanisms are found to be triggered
either (i) by a stretch of the NpheH bond, which leads to an H-transfer to the ring, or (ii) by specific backbone
amide distortions. The potential energy surfaces of the NAPA conformers along these critical pathways have
been characterized more accurately using the coupled cluster doubles (CC2) method and shown to exhibit
barriers that can be overcome with moderate excess energies. These results analyzed in the light of the
experimental findings enabled us to assign the short lifetime of NAPA B conformer to a number of easily
accessible exit channels from the initial pi pi* surface, most importantly the one involving a transfer of
electronic excitation to an n pi* surface, induced by distortions of the backbone peptide bond.
[2008-054T] SYMTCOB
Porteur : H. Alloul
Thème 4
Growth and characterisation of Li(x)CoO(2) single crystals
Auteurs : L. Pinsard-Gaudart,V.C. Ciomaga, O. Dragos, R. Guillot, N. Dragoe
Réf. : JOURNAL OF CRYSTAL GROWTH Volume: 334 Issue: 1 DOI: 10.1016/j.jcrysgro.2011.07.024
Published: NOV 1 2011
28/02/2013
31
PUBLICATIONS
PROJETS 2008
Centimetre-size single crystals of LiCoO(2) were successfully grown using a floating-zone method associated
with an image furnace. A high-pressure oxygen atmosphere and a relatively small growth speed were found
necessary to prevent the formation of impurity phases in the grown crystal. A single crystal with a reduced
amount of lithium was obtained by means of the chemical de-lithiation process using as grown LiCoO(2) single
crystal as the starting material. Growth conditions together with magnetic and structural properties of these
crystals are discussed here. (C) 2011 Elsevier B.V. All rights reserved.
Na-23 NMR study of sodium order in NaxCoO2 with 22 K Neel
temperature
Auteurs : Alloul H.; Mukhamedshin I. R.; Dooglav A. V.; et al.
Réf. : PHYSICAL REVIEW B
Volume: 85
Issue: 13
10.1103/PhysRevB.85.134433 Published: APR 20 2012
DOI:
Pas d'abstract
[2008-055T] GRAMINE
Porteur : Sophie Noël
Axe C
Conductive-probe AFM characterization of graphene sheets bonded
to gold surfaces
Auteurs : Hauquier, Fanny; Alamarguy, David; Viel, Pascal; Noel, Sophie; Filoramo, Arianna; Huc,
Vincent; Houze, Frederic; Palacin, Serge
Réf. : APPLIED SURFACE SCIENCE, 258 (7):2920-2926; 10.1016/j.apsusc.2011.10.152 JAN 15 2012
Conducting probe atomic force microscopy (CP-AFM) has been used to perform mechanical and electrical
experiments on graphene layers bonded to polyaminophenylene (PAP) films grafted on gold substrates. This
technique is a new approach for the characterization of graphene sheets and represents a complementary tool to
Raman spectroscopy. The combination of friction and electrical imaging reveals that different stacked graphene
sheets have been successfully distinguished from each other and from the underlying PAP films. Lateral force
microscopy has shown that the friction is greatly reduced on graphene sheets in comparison with the organic
coating. The electrical resistance images show very different local conduction properties which can be linked to
the number of underlying graphene sheets. The resistance decreases very slowly when the normal load increases.
Current-voltage curves display characteristics of metal-molecule-metal junctions. (C) 2011 Elsevier B.V. All
rights reserved.
28/02/2013
32
PUBLICATIONS
PROJETS 2008
[2008-056T] FLAG
Porteur : Bertrand Poumellec
Thème 7
Anatomy of a femtosecond laser processed silica waveguide
[Invited]
Auteurs : Canning J.; Lancry M.; Cook K.; et al.
Réf. : OPTICAL MATERIALS EXPRESS Volume: 1 Issue: 5 Pages: 998-1008 Published: SEP 1 2011
Waveguides are inscribed through densification of the surrounding region of a damage induced channel created
by femtosecond irradiation within silica. Single mode propagation at 1.5 mu m is obtained below the damage
region whilst at shorter wavelengths guidance is only observed away on either side of the region. The quasiperiodic nanostructure that is induced can explain the mode profile elongation observed with polarised light at
45. The origin of this guidance area is explored using SEM analysis, which reveals nanoporous regions within
laser track structure above and below the densified region where 1.5 mu m propagates. Shorter wavelength light
is not supported in this area. (C) 2011 Optical Society of America
Dependence of the femtosecond laser refractive index change
thresholds on the chemical composition of doped-silica glasses
Auteurs : Lancry, M; Poumellec, B; Chahid-Erraji, A; Beresna, M; Kazansky, PG
Réf. : OPTICAL MATERIALS EXPRESS, 1 (4):711-723; AUG 1 2011
The refractive index changes in doped silica are investigated. We observed that the permanent isotropic index
change threshold (T1) is not significantly dependent on the doping. We show that strong birefringence
(permanent linear birefringence) exists in doped silica but its threshold (T2) exhibits significant dependence on
the used dopants. In our conditions, comparing with silica (0.31 mu J/pulse here), for 1.5 at% Ge-doped silica the
T2 threshold is smaller (0.14 +/- 0.05 mu J/pulse). For a silica doped with 0.3 at% of fluorine, T2 is close to 1.20
+/- 0.05 mu J/pulse. An interpretation is given not only about threshold variation but also about RIC for energies
beyond. It is based on the overcoming of relaxation time in the volume interaction. (C) 2011 Optical Society of
America
Modification thresholds in femtosecond laser processing of pure
silica: review of dependencies on laser parameters [Invited]
Auteurs : Poumellec, B; Lancry, M; Chahid-Erraji, A; Kazansky, PG
Réf. : OPTICAL MATERIALS EXPRESS, 1 (4):766-782; AUG 1 2011
This review allows better defining the domains of macroscopic effects produced by the femtosecond laser
irradiation in pure silica according to the laser parameters. (C) 2011 Optical Society of America
28/02/2013
33
PUBLICATIONS
PROJETS 2008
Time-resolved plasma measurements in Ge-doped silica exposed to
infrared femtosecond laser
Auteurs : Lancry M.; Groothoff N.; Poumellec B.; et al
Volume: 84
Issue: 24
10.1103/PhysRevB.84.245103 Published: DEC 8 2011
DOI:
Using a time-resolved interferometric technique, we study the laser-induced carrier-trapping dynamics in SiO(2)
and Ge-doped SiO(2). The fast trapping of electrons in the band gap is associated with the formation of selftrapped excitons (STE). The STE trapping is doping dependent in SiO(2). The mean trapping time of electrons
excited in the conduction band was found to be significantly lower in Ge-doped silica (75 +/- 5 fs) when
compared to pure silica (155 +/- 5 fs). At our concentration level, this indicates that the plasma properties are
determined by the presence of easily ionizable states such as the presence of Ge atoms in the glass network.
Therefore, we suggest that in Ge-doped silica there exist an additional trapping pathway that leads to a
significantly faster excitons trapping and a higher plasma density when compared to undoped silica.
Gold Nanoparticles Reshaped by Ultrafast Laser Irradiation Inside a
Silica-Based Glass, Studied Through Optical Properties
Auteurs : Fan Chaxing; Poumellec Bertrand; Zeng Huidan; et al.
Réf. : JOURNAL OF PHYSICAL CHEMISTRY C Volume: 116
10.1021/jp203408y Published: FEB 2 2012
Issue: 4
Pages: 2647-2655
DOI:
Quasi-spherical or quasi-rod gold nanoparticles with an average diameter of 3.8 nm are randomly precipitated in
a silica-based glass by a heat-treatment method. After ultrafast laser irradiation at 400 and 620 nm, optical
absorption, birefringence, and dichroism measurements are performed to investigate the modification of gold
nanoparticles shape. Theoretical simulations have been carried out to interpret the experimental results. We
suggest that a small fraction of gold nanospheres are transformed mainly into nanodisks but also into nanorods
oriented along the laser polarization for both fs laser wavelength. Absorption simulation suggests that they have
an aspect ratio of 1.8 and 0.5, respectively, for fs laser irradiation at 400 nm. For 620 nm, the aspect ratio of the
nanorods increases and the one of the nanodisks decreases. In such a way, we demonstrate that reshaping of gold
nanoparticles, i.e. a property that was previously found for silver nanoparticles in multicomponent glass is also
possible. By imaging the distribution of the birefringence according to the probe wavelength, we show that
nanopartides are aligned into nanorods mainly out of irradiated volume and into nanopellets mainly in the
irradiated volume.
Oriented creation of anisotropic defects by IR femtosecond laser
scanning in silica
Auteurs : Lancry, M.; Poumellec, B.; Desmarchelier, R.; Bourguignon, B.
Réf. : OPTICAL MATERIALS EXPRESS Volume: 2
2012
Issue: 12
Pages: 1809-1821
Published: DEC 1
Irradiation of non-luminescent silica with polarized IR femtosecond laser light produced a significant amount of
luminescent defects. We have investigated the properties of luminescence produced by the defects using UVVUV excitation experiment depending on the relative orientation of the laser polarization and its scanning
direction. Silicon Oxygen Deficient Center (SiODC) is identified. SiODC related luminescence is much stronger
28/02/2013
34
PUBLICATIONS
PROJETS 2008
when the excitation polarization is parallel to the sample scanning direction and moved at low velocity,
regardless of the writing polarization direction. This indicates that the creation of this anisotropic defect is
oriented by the movement of the femtosecond laser beam. (C)2012 Optical Society of America
Three-dimensional photoprecipitation of oriented LiNbO3-like
crystals in silica-based glass with femtosecond laser irradiation
Auteurs : Fan, Chaxing; Poumellec, Bertrand; Lancry, Matthieu; He, Xuan; Zeng, Huidan; ErrajiChahid, Abdel; Liu, Qiming; Chen, Guorong
Réf. : OPTICS LETTERS Volume: 37 Issue: 14 Pages: 2955-2957 Published: JUL 15 2012
We demonstrate crystals (LiNbO3-like) that were space-selectively nucleated and grown in the bulk of silicabased glass by femtosecond laser irradiation at a high repetition rate (typ. 300 kHz). Oriented crystals with their
polar axis mostly aligned with or perpendicular to the laser scanning direction have been fabricated by
manipulation of the temperature gradient in adjusting the laser parameters. The mechanism for the orientation of
femtosecond laser-induced crystallization is briefly discussed. (C) 2012 Optical Society of America
[2008-057T] PAO
Porteur : Jean-Jacques Greffet
Thème 7
Dielectric gratings for wide-angle, broadband absorption by thin
film photovoltaic cells
Auteurs : Laroche M ; Greffet JJ; R. Esteban
Optical management is essential to increase absorption in thin photovoltaic cells. In this article, full
electromagnetic simulations show that a back mirror and a one-dimensional front SiC sawtooth grating of similar
to 1 mu m dimensions can significantly increase absorption in a thin layer under light concentration. A 50 nm
thick GaSb active layer in the described configuration absorbs similar to 66% of the incident solar photons above
the band gap for a concentration equivalent to a numerical aperture NA=1/root 2. This absorption represents a
similar to 76% or 26% increase over the same structure but with the grating removed or substituted by an ideal
antireflection coating, respectively. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3512898]
Optical Patch Antennas for Single Photon Emission Using Surface
Plasmon Resonances
Auteurs : Esteban, R. Teperik, TV. Jean-Jacques Greffet
28/02/2013
35
PUBLICATIONS
PROJETS 2008
Single photon sources can greatly benefit from specially designed structures that modify the properties of the
photon emitter. Dielectric cavities are often discussed, but they require a compromise between the spectral width
and Purcell factor. In this Letter, we introduce plasmonic cavities as promising alternatives. We first study how
the emitter couples with the modes of such structures. We then show how a patch antenna configuration
simultaneously presents a large Purcell factor, collection efficiency, and spectral width.
Experimental study of hot spots in gold/glass nanocomposite films
by photoemission electron microscopy
Auteurs : Awada, C.; Barbillon, G.; Charra, F.; Douillard, L.; Greffet, J. -J.
Réf. : PHYSICAL REVIEW B, 85 (4):10.1103/PhysRevB.85.045438 JAN 24 2012
In this paper, an experimental study of hot spots in gold/dielectric films using photoemission electron
microscopy is reported. This technique allows a characterization of the statistical optical properties with
unprecedented accuracy in the 800- to 1040-nm range. Theoretical predictions of the scaling theory on the
number and intensity wavelength dependences of hot spots in the near-infrared are confirmed. Statistical
properties of the intensity distribution, spectral behavior, and spatial localization of the hot spots are reported.
Nanoscale magnetic field mapping with a single spin scanning probe
magnetometer
Auteurs : Rondin L.; Tetienne J. -P.; Spinicelli P.; et al.
10.1063/1.3703128 Published: APR 9 2012
Issue: 15
DOI:
We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique
on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic
force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large
off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques
are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative
nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and
spintronics. (C) 2012 American Institute of Physics. [http://dx.doi. org/10.1063/1.3703128]
[2008-058T] FemtoARPES
Porteur : Marino Marsi
Thème 4
Coherent Phonon Coupling to Individual Bloch States in
Photoexcited Bismuth
Auteurs : Papalazarou, E.; Faure, J.; Mauchain, J.; Marsi, M.; Taleb-Ibrahimi, A.; Reshetnyak, I.; van
Roekeghem, A.; Timrov, I.; Vast, N.; Arnaud, B.; Perfetti, L.
28/02/2013
36
PUBLICATIONS
PROJETS 2008
Réf. : PHYSICAL REVIEW LETTERS Volume: 108 Issue: 25
10.1103/PhysRevLett.108.256808 Published: JUN 20 2012
DOI:
We investigate the temporal evolution of the electronic states at the bismuth (111) surface by means of time- and
angle-resolved photoelectron spectroscopy. The binding energy of bulklike bands oscillates with the frequency
of the A(1g) phonon mode, whereas surface states are insensitive to the coherent displacement of the lattice. A
strong dependence of the oscillation amplitude on the electronic wave vector is correctly reproduced by ab initio
calculations of electron-phonon coupling. Besides these oscillations, all the electronic states also display a
photoinduced shift towards higher binding energy whose dynamics follows the evolution of the electronic
temperature.
Giant Anisotropy of Spin-Orbit Splitting at the Bismuth Surface
Auteurs : Ohtsubo, Y.; Mauchain, J.; Faure, J.; Papalazarou, E.; Marsi, M.; Le Fevre, P.; Bertran, F.;
Taleb-Ibrahimi, A.; Perfetti, L.
Réf. : PHYSICAL REVIEW LETTERS Volume: 109 Issue: 22
10.1103/PhysRevLett.109.226404 Published: NOV 27 2012
DOI:
We investigate the bismuth (111) surface by means of time and angle resolved photoelectron spectroscopy. The
parallel detection of the surface states below and above the Fermi level reveals a giant anisotropy of the spinorbit spitting. These strong deviations from the Rashba-like coupling cannot be treated in k.p perturbation
theory. Instead, first principles calculations could accurately reproduce the experimental dispersion of the
electronic states. Our analysis shows that the giant anisotropy of the spin-orbit splitting is due to a large out-of
plane buckling of the spin and orbital texture.
Ultrafast Surface Carrier Dynamics in the Topological Insulator
Bi2Te3
Auteurs : Hajlaoui, M.; Papalazarou, E.; Mauchain, J.; Lantz, G.; Moisan, N.; Boschetto, D.; Jiang, Z.;
Miotkowski, I.; Chen, Y. P.; Taleb-Ibrahimi, A.; Perfetti, L.; Marsi, M.
Réf. : NANO LETTERS Volume: 12 Issue: 7 Pages: 3532-3536 DOI: 10.1021/nl301035x Published:
JUL 2012
We discuss the ultrafast evolution of the surface electronic structure of the topological insulator Bi2Te3
following a femtosecond laser excitation. Using time and angle-resolved photoelectron spectroscopy, we provide
a direct real-time visualization of the transient carrier population of both the surface states and the bulk
conduction band. We find that the thermalization of the surface states is initially determined by interband
scattering from the bulk conduction band, lasting for about 0.5 ps; subsequently, few picoseconds are necessary
for the Dirac cone non-equilibrium electrons to recover a Fermi-Dirac distribution, while their relaxation extends
over more than 10 ps. The surface sensitivity of our measurements makes it possible to estimate the range of the
bulk-surface interband scattering channel, indicating that the process is effective over a distance of 5 nm or less.
This establishes a correlation between the nanoscale thickness of the bulk charge reservoir and the evolution of
the ultrafast carrier dynamics in the surface Dirac cone.
28/02/2013
37
PUBLICATIONS
PROJETS 2008
Ultrafast filling of an electronic pseudogap in an incommensurate
crystal
Auteurs : Brouet, V.; Mauchain, J.; Papalazarou, E.; Faure, J.; Marsi, M.; Lin, P. H.; Taleb-Ibrahimi, A.; Le
Fevre, P.; Bertran, F.; Cario, L.; Janod, E.; Corraze, B.; Phuoc, V. Ta; Perfetti, L.
Issue: 4
10.1103/PhysRevB.87.041106 Published: JAN 28 2013
DOI:
We investigate the quasiperiodic crystal (LaS)(1.196)VS2 by angle and time resolved photoemission
spectroscopy. The dispersion of electronic states is in qualitative agreement with the band structure calculated
for the VS2 slab without incommensurate distortion. Nonetheless, the spectra display a temperature dependent
pseudogap instead of quasiparticle crossing. The sudden photoexcitation at 50 K induces a partial filling of the
electronic pseudogap within less than 80 fs. The electronic energy flows into the lattice modes on a comparable
time scale. We attribute this surprisingly short time scale to a very strong electron-phonon coupling to the
incommensurate distortion. This result sheds light on the electronic localization arising in aperiodic structures
and quasicrystals. DOI: 10.1103/PhysRevB.87.041106
[2008-060T] MeMoFri
Porteur : Liliane Leger
Thème 3
Contact Angle and Contact Angle Hysteresis Measurements Using
the Capillary Bridge Technique
Auteurs : Restagno, F. Poulard, C. Cohen, C. Vagharchakian, L. Leger, L
Réf. : LANGMUIR 25 (2009) 11188-11196
A new experimental technique is proposed to easily measure both advancing and receding contact angles of a
liquid on a solid surface, with unprecedented accuracy. The technique is based on the analysis of the evolution of
a capillary bridge formed between a liquid bath and a solid surface (which needs to be spherical) when the
distance between the surface and the liquid bath is slowly varied. The feasibility of the technique is demonstrated
using a low-energy perfluorinated Surface with two different test liquids (water and hexadecane). A detailed
description of both experimental procedures and computational modeling are given, allowing one to determine
contact angle Values. It is shown that the origin of the high accuracy of this technique relies on the fact that the
con tact angles are automatically averaged over the whole periphery of the contact. This method appears to be
particularly adapted to the characterization Of surfaces with very low contact angle hysteresis.
Incidence of the molecular organization on friction at soft polymer
interfaces
Auteurs : Cohen, Celine; Restagno, Frederic; Poulard, Christophe; Leger, Liliane
28/02/2013
38
PUBLICATIONS
PROJETS 2008
Réf. : SOFT MATTER 7 (18): 8535-8541 10.1039/c1sm05874f 2011
Polymer molecules strongly anchored to a solid substrate and interdigitated into bulk crosslinked elastomer have
been shown recently to efficiently promote adhesion and friction between substrate and elastomer. Concerning
friction, the regime of low surface coverage in surface anchored chains has been fully and quantitatively
accounted for by the pull off mechanisms, where individual chains are dynamically extracted from the elastomer.
Then, the stretching energy of these chains dominates the friction losses. We focus here on the dense surface
coverage regime. We present systematic experiments performed on the polydimethylsiloxane (PDMS) - silica
system, and determine molecular weight and sliding velocity dependences of the friction stress. We show that
the friction is dominated by the shear thinning of the grafted layer confined between the elastomer and the
substrate, and responding to the shear solicitation like a melt, but with very long relaxation times. We also show
that the friction stress appears highly sensitive to the molecular organization inside the surface anchored polymer
layer, comparing end grafted and strongly adsorbed layers having otherwise the same molecular characteristics
(molecular weight of the chains, and thickness of the surface anchored layer).
Synthesis of well-defined poly(dimethylsiloxane) telechelics having
nitrobenzoxadiazole fluorescent chain-ends via thiol-ene coupling
Auteurs : Cohen Celine; Damiron Denis; Ben Dkhil Sadok; et al.
Réf. : JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Volume: 50 Issue: 9 Pages:
1827-1833 DOI: 10.1002/pola.25952 Published: MAY 1 2012
Well-defined PDMS telechelics having nitrobenzoxadiazole (NBD) fluorescent probes covalently attached at
both chain-ends were prepared in two steps and a series of fractionation procedures starting from commercially
available divinyl-terminated PDMS having a broad molar mass dispersity. First, thiol-ene coupling between 6mercapto-1-hexanol and vinyl chain-ends allowed the formation of dihydroxy-terminated PDMS telechelics
through the formation of a thioether linkage. The resulting material was then sequentially fractionated using
dichloromethane/methanol mixtures to afford several well-defined dihydroxy-terminated PDMS fractions having
sharp distributions of molar masses (Mn = 99.5158 kDa and D < 1.2). The NBD fluorescent probes were then
attached at both chain-ends by N,N'-dicyclohexylcarbodiimide/4-(dimethylamino)pyridine esterification
coupling between the hydroxyl groups and 6-(7-nitrobenzofurazan-4-ylamino)hexanoic acid. The resulting
fluorescent PDMS telechelics were characterized by SEC, 1H NMR, UVvisible, and fluorescence
spectroscopies. These materials are suitable probes to investigate the dynamics of polymer chains in bulk or at
interfaces by the fringe pattern fluorescent recovery after photobleaching technique. (C) 2012 Wiley Periodicals,
Inc. J Polym Sci Part A: Polym Chem, 2012
Wetting and Dewetting Transition: An Efficient Toolbox for
Characterizing Low-Energy Surfaces
Auteurs : Cohen, C. Restagno, F. Poulard, C. Leger, L.
Réf. : LANGMUIR 26 (2010) 15345-15349
The capillary bridge formed between a solid spherical surface and an infinite liquid bath is an efficient technique
for characterizing the adhesion property of a solid surface. When the solid surface is pulled out of the liquid at a
sufficiently high velocity, a thin liquid film is deposited on the solid and drains more slowly than the central
capillary bridge. The retraction kinetics of this "pancake" and the critical velocity above which it appears are
studied as a function of the viscosity of the liquid or the wettability of the solids. The dynamics of the liquid film
follows the classical law of dynamic dewetting. This makes the capillary bridge test, used in the dynamical
regime, a very efficient tool for discriminating between antiadhesive coatings.
28/02/2013
39
PUBLICATIONS
PROJETS 2008
[2008-061T] MINIATOM
Porteur : Philippe Bouyer
Thème 1
Light-pulse atom interferometry in microgravity
Auteurs : Stern, G. Battelier, B. Geiger, R. Varoquaux, G. Villing, A. Moron, F. Carraz, O. Zahzam, N.
Bidel, Y. Chaibi, W. Dos Santos, FP. Bresson, A. Landragin, A. Bouyer, P
Réf. : EUROPEAN PHYSICAL JOURNAL D 57 (2009) 87-94
We describe the operation of a light pulse interferometer using cold Rb-87 atoms in reduced gravity. Using a
series of two Raman transitions induced by light pulses, we have obtained Ramsey fringes in the low gravity
environment achieved during parabolic flights. With our compact apparatus, we have operated in a regime which
is not accessible on ground. In the much lower gravity environment and lower vibration level of a satellite, our
cold atom interferometer could measure accelerations with a sensitivity orders of magnitude better than the best
ground based accelerometers and close to proven spaced-based ones.
Frequency doubled 1534nm laser system for potassium laser
cooling
Auteurs : Stern G, Allard B, Robert-De-Saint-Vincent M, Brantut JP , Battelier B, Bourdel T, Bouyer P
Réf. : APPLIED OPTICS 49 (2010)
We demonstrate a compact laser source suitable for trapping and cooling potassium. By frequency doubling a
fiber laser diode at 1534nm in a waveguide, we produce 767nm laser light. A current modulation of the diode
allows us to generate the two required frequencies for cooling in a simple and robust apparatus. We successfully
used this laser source to trap K-39. (c) 2010 Optical Society of America
[2008-062T] DYNANEX
Porteur : Lionel Poisson
Thème 2
Photoionization of 2-pyridone and 2-hydroxypyridine
Auteurs : Poully, JC. Schermann, JP. Nieuwjaer, N. Lecomte, F. Gregoire, G. Desfrancois, C. Garcia,
GA. Nahon, L. Nandi, D. Poisson, L. Hochlaf, M
Réf. : PHYSICAL CHEMISTRY CHEMICAL PHYSICS 12 (2010) 3566-3572
28/02/2013
40
PUBLICATIONS
PROJETS 2008
We studied the photoionization of 2-pyridone and its tautomer, 2-hydroxypyridine by means of VUV
synchrotron radiation coupled to a velocity map imaging electron/ion coincidence spectrometer. The
photoionization efficiency (PIE) spectrum is composed of steps. The state energies of the [2-pyridone](+) cation
in the (X) over tilde ground and (A) over tilde excited electronic states, as well as of the [2-hydroxypyridine](+)
cation in the electronic ground state, are determined. The slow photoelectron spectra (SPES) are dominated by
the 0(0)(0) transitions to the corresponding electronic states together with several weaker bands corresponding to
the population of the pure or combination vibrational bands of the cations. These vibrationally-resolved spectra
compare very well with state-of-the-art calculations. Close to the ionization thresholds, the photoionization of
these molecules is found to be mainly dominated by a direct process whereas the indirect route (autoionization)
may contribute at higher energies.
A two-step ICT process for solvatochromic betaine pyridinium
revealed by ultrafast spectroscopy, multivariate curve resolution,
and TDDFT calculations
Auteurs : Aloise Stephane; Pawlowska Zuzanna; Ruckebusch Cyril; et al.
Réf. : PHYSICAL CHEMISTRY CHEMICAL PHYSICS Volume: 14
10.1039/c2cp22254j Published: 2012
Issue: 6
Pages: 1945-1956
DOI:
This work deals with the photophysics of a pyridinium betaine, 2-pyridin-1-yl-1H-benzimidazole (SBPa), based
on a combination of steady-state, femtosecond photoionization (gas phase) and femtosecond transient absorption
(solution) spectroscopic measurements, supported by (LR)-PCM-(TD)DFT calculations. Preliminary and new
electrochemical results have revealed a strongly negative solvatochromic charge transfer (CT) absorption due to
a S-0 -> S-2 vertical transition and a weakly-solvatochromic emission due to S-1 -> S-0 transition. Advanced
TDDFT optimizations of the Franck-Condon states S-2(FC) and S-1(FC) led to two additional CT levels with
planar geometry, S-2(CT) and S-1(CT), respectively, allowing prediction of a two-step photoinduced ICT
process, i.e., S-0 -> S-2(FC) and S-2(CT) -> S-1(CT), separated by a S-2(FC) -> S-2(CT) back charge transfer
relaxation. While the pyridinium ring is the acceptor group in both steps, two different donor groups, the
benzene ring and the imidazole bridge, are involved in the excitation and internal conversion processes,
respectively. Femtosecond transient absorption experiments supported by MCR-ALS decomposition confirmed
indeed the contribution of two distinct CT states in the photophysics of SBPa: following excitation to the S2(CT) state, ultrafast production of the emissive S-1 state (the only channel observable in the gas phase) was
observed to occur in competition with a further ICT process toward the S-1(CT) state, with a time constant
ranging from 300 fs to 20 ps depending on the solvent. While in aprotic media this ICT process was found to be
purely solvent controlled (double polarity and viscosity dependency), in protic solvents, the influence of the
hydrogen bond network has to be taken into account. Comparison with data obtained for a pre-twisted SBPa
analogue led us to exclude the presence of any large-amplitude geometrical change during ICT. Analyzing the
solvent dependency using the power law approach, we concluded that the S-1(CT) state decays essentially
through IC in the 3-40 ps time range whereas the emissive S-1 state decays within 130-260 ps via IC, ISC and
fluorescence.
Femtosecond dynamics of cyclopropenylidene, c-C3H2
Auteurs : Hemberger Patrick; Koehler Juliane; Fischer Ingo; et al.
Réf. : PHYSICAL CHEMISTRY CHEMICAL PHYSICS Volume: 14
10.1039/c2cp23728h Published: 2012
Issue: 18
Pages: 6173-6178
DOI:
The photophysics of the B B-1(1) state of isolated cyclopropenylidene, c-C3H2, has been studied by
femtosecond time-resolved photoionisation and photoelectron spectroscopy. The carbene was produced by flash
28/02/2013
41
PUBLICATIONS
PROJETS 2008
pyrolysis of 3-chlorocycloprop-1-ene. The bands at 266.9 nm and 264.6 nm have been investigated. The excited
state deactivates in a two step process. The first time constant of less than 50 fs corresponds most likely to a
nonradiative transition to the A-state, the second one on the order of 200 fs describes the internal conversion to
the electronic ground state. The data are compared to those measured for the chlorinated carbene c-C3HCl. In the
photoelectron spectrum of c-C3H2 resonances were observed which can be assigned to members of a Rydberg dseries.
[2008-063T] SAMNANO
Porteur : Vladimir Esaulov
Thème 2
UPS, XPS, and NEXAFS Study of Self-Assembly of Standing 1,4Benzenedimethanethiol SAMs on Gold
Auteurs : Pasquali, L; Terzi, F; Seeber, R; Nannarone, S; Datta, D; Dablemont, C; Hamoudi, H; Canepa,
M; Esaulov, VA
Réf. : LANGMUIR 27 (8): 4713-4720 APR 19 2011
We report a study of the self-assembly of 1,4-benzenedimethanethiol monolayers on gold formed in n-hexane
solution held at 60 degrees C for 30 mm and in dark conditions. The valence band characteristics, the thickness
of the layer, and the orientation of the molecules were analyzed at a synchrotron using high resolution
photoelectron spectroscopy and near edge X-ray adsorption spectroscopy. These measurements unambiguously
attest the formation of a single layer with molecules arranged in the upright position and presenting a free -SH
group at the outer interface. Near edge X-ray absorption fine structure (NEXAFS) measurements suggest that the
molecular axis is oriented at 24 degrees with respect to the surface normal. In addition, valence band features
could be successfully associated to specific molecular orbital contributions thanks to the comparison with
theoretically calculated density of states projected on the different molecular units.
[2008-064T] THERMETG
Porteur : Bérengère Dubrulle
Thème 3
Relevance of visco-plastic theory in a multi-directional
inhomogeneous granular flow
Auteurs : Cortet, PP. Bonamy, D. Daviaud, F. Olivier Dauchot. Bérengère Dubrulle. Renouf, M
Réf. : EPL 88 (2009) 30009
28/02/2013
42
PUBLICATIONS
PROJETS 2008
We confront a recent visco-plastic description of dense granular flows (Jop P. et al., Nature, 441 (2006) 727)
with multi-directional inhomogeneous steady flows observed in non-smooth contact dynamics simulations of 2D
half-filled rotating drums. Special attention is paid to check separately the two underlying fundamental
statements into which the considered theory can be recast, namely i) a single relation between the invariants of
stress and strain rate tensors and ii) the alignment between these tensors. Interestingly, the first prediction is
fairly well verified over more than four decades of small strain rate, from the surface rapid flow to the quasistatic creep phase, where it is usually believed to fail because of jamming. On the other hand, the alignment
between stress and strain rate tensors is shown to fail over the whole flow, what yields an apparent violation of
the visco-plastic rheology when applied without care. In the quasi-static phase, the particularly large
misalignment is conjectured to be related to transient dilatancy effects. Copyright (C) EPLA, 2009
Experimental Evidence of a Phase Transition in a Closed Turbulent
Flow
Auteurs : Cortet PP ; Chiffaudel A ; Daviaud F ; Bérengère Dubrulle
We experimentally study the susceptibility to symmetry breaking of a closed turbulent von Karman swirling
flow from Re 150 to Re similar or equal to 10(6). We report a divergence of this susceptibility at an intermediate
Reynolds number Re = Re-chi similar or equal to 90 000 which gives experimental evidence that such a highly
space and time fluctuating system can undergo a "phase transition.'' This transition is furthermore associated
with a peak in the amplitude of fluctuations of the instantaneous flow symmetry corresponding to intermittencies
between spontaneously symmetry breaking metastable states.
Susceptibility divergence, phase transition and multistability of a
highly turbulent closed flow
Auteurs : Cortet, PP; Herbert, E; Chiffaudel, A; Daviaud, F; Dubrulle, B; Padilla, V
Réf. : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT
5468/2011/07/P07012 JUL 2011
10.1088/1742-
Using time series of stereoscopic particle image velocimetry data, we study the response of a turbulent von
Karman swirling flow to a continuous breaking of its forcing symmetry. Experiments are carried over a wide
Reynolds number range, from the laminar regime at Re = 10(2) to the highly turbulent regime near Re = 10(6).
We show that the flow symmetry can be quantitatively characterized by two scalars, the global angular
momentum I and the mixing layer altitude z(s), which are shown to be statistically equivalent. Furthermore, we
report that the flow response to small forcing asymmetry is linear, with a slope depending on the Reynolds
number: this response coefficient increases non-monotonically from small to large Reynolds number and
presents a divergence at a critical Reynolds number Re(c) = 40 000 +/- 5000. This divergence coincides with a
change in the statistical properties of the instantaneous flow symmetry I(t): its pdf changes from Gaussian to
non-Gaussian with multiple maxima, revealing metastable non-symmetrical states. For symmetric forcing, a
peak of fluctuations of I(t) is also observed at Re(c): these fluctuations correspond to time intermittencies
between metastable states of the flow which, contrary to the very-long-time-averaged mean flow, spontaneously
and dynamically break the system symmetry. We show that these observations can be interpreted in terms of
divergence of the susceptibility to symmetry breaking, revealing the existence ofa phase transition. An analogy
with the ferromagnetic-paramagnetic transition in solid-state physics is presented and discussed.
28/02/2013
43
PUBLICATIONS
PROJETS 2008
[2008-065T] Glasdespin
Porteur : Isabelle Mirebeau
Thème 4
Magnetic order in Tb2Sn2O7 under high pressure: From ordered
spin ice to spin liquid and antiferromagnetic order
Auteurs : Isabelle Mirebeau. Goncharenko, I. Cao, H. Forget, A
We have studied the Tb2Sn2O7 ordered spin ice by neutron diffraction under an isotropic pressure of 4.6 GPa,
combined with a stress of 0.3(1) GPa. Measurements down to a temperature of 0.06 K and up to 100 K probe the
effect of pressure both on ground state and spin fluctuation in the paramagnetic region. In the pressure-induced
ground state, the ordered spin ice structure with a k(0)=0 propagation vector persists, but it coexists with a
structure with k(1)=(0,0,1). The ordered moment at 0.06 K is reduced, suggesting that pressure also enhances the
spin liquid fluctuations at T similar to 0. In the paramagnetic region, applying pressure changes the short-range
spin correlations and suppresses the ferromagnetic correlations. The influence of pressure is discussed
considering both isotropic pressure and stress effects.
Field evolution of the magnetic structures in Er2Ti2O7 through the
critical point
Auteurs : Cao, HB. Isabelle Mirebeau. Gukasov, A. Bonville, P. Decorse, C
Réf. : PHYSICAL REVIEW B V 82 (2010) 104431
We have measured neutron-diffraction patterns in a single-crystal sample of the pyrochlore compound Er2Ti2O7
in the antiferromagnetic phase (T=0.3 K), as a function of the magnetic field, up to 6 T, applied along the [110]
direction. We determine all the characteristics of the magnetic structure throughout the critical point at H-c=2 T.
As a main result, all Er moments align along the field at H-c and their values reach a minimum. Using a foursublattice self-consistent calculation, we show that the evolution of the magnetic structure and the value of the
critical field are rather well reproduced using the same anisotropic exchange tensor as that accounting for the
local paramagnetic susceptibility. In contrast, an isotropic exchange tensor does not yield the correct moment
variations through the critical point. The model also accounts semiquantitatively for other experimental data
obtained in previous works, such as the field dependence of the heat capacity, energy of the dispersionless
inelastic modes and transition temperature.
Field-induced magnetic structures in Tb2Ti2O7 at low
temperatures: From spin-ice to spin-flip structures
Auteurs : Sazonov AP ; Gukasov A ; Isabelle Mirebeau ; Cao H ;Bonville P ; Grenier B
We studied the field-induced magnetic structures of the Tb2Ti2O7 pyrochlore by single-crystal neutron
diffraction with a magnetic field applied along a [110] axis, focusing on the influence of a small misalignment.
28/02/2013
44
PUBLICATIONS
PROJETS 2008
Both induced magnetic structures with k = 0 and k = (0,0,1) propagation vectors are found to be sensitive to the
misalignment, which controls the magnitude and orientation of the Tb moments involved in the beta chains, with
local [111] anisotropy axis perpendicular to the field. For k = 0, spin-icelike structures are observed for a
misalignment of a few degrees whereas other structures, where the Tb-beta moments flip by "melting" on the
field axis, occur when the field is perfectly aligned. The field evolution of the k = 0 structure is well reproduced
by a molecular field model with anisotropic exchange. We give a complete symmetry analysis of the k = 0 and k
= (0,0,1) magnetic structures, both being described by the basis functions of single irreducible representations.
Neutron diffraction study of the chiral magnet MnGe
Auteurs : Makarova O. L.; Tsvyashchenko A. V.; Andre G.; et al.
Volume: 85
Issue: 20
10.1103/PhysRevB.85.205205 Published: MAY 14 2012
DOI:
The magnetic structure of cubic MnGe has been determined by powder neutron diffraction. MnGe has a helical
spin structure with a propagation vector k = (0,0, zeta), where zeta = 0.107(5) just below the transition
temperature T-N = 170 K. The zeta value increases upon cooling and locks in to the value of 0.167(4) below 30
K. The moment value is 2.3(5)mu(B) at 2 K. The onset of the magnetic order is connected with a symmetry
lowering from cubic to orthorhombic.
[2008-066T] OXY SPINTRONICS
Porteur : Agnès Barthélémy
Thème 5
Towards Two-Dimensional Metallic Behavior at LaAlO3/SrTiO3
Interfaces
Auteurs : Copie, O. Garcia, V. Bodefeld, C. Carretero, C. Bibes, M. Herranz, G. Jacquet, E. Maurice, JL.
Vinter, B. Fusil, S. Karim Bouzehouane. Jaffres, H. Barthelemy, A
Using a low-temperature conductive-tip atomic force microscope in cross-section geometry we have
characterized the local transport properties of the metallic electron gas that forms at the interface between
LaAlO3 and SrTiO3. At low temperature, we find that the carriers do not spread away from the interface but are
confined within similar to 10 nm, just like at room temperature. Simulations taking into account both the large
temperature and electric-field dependence of the permittivity of SrTiO3 predict a confinement over a few nm for
sheet carrier densities larger than similar to 6x10(13) cm(-2). We discuss the experimental and simulations
results in terms of a multiband carrier system. Remarkably, the Fermi wavelength estimated from Hall
measurements is similar to 16 nm, indicating that the electron gas in on the verge of two dimensionality.
28/02/2013
45
PUBLICATIONS
PROJETS 2008
Ferroelectric Control of Spin Polarization
Auteurs : Garcia, V. Bibes, M. Bocher, L. Valencia, S. Kronast, F. Crassous, A. Moya, X. EnouzVedrenne, S. Gloter, A. Imhoff, D. Deranlot, C. Mathur, ND. Fusil, S. Karim Bouzehouane. Barthelemy,
A
Réf. : SCIENCE 327 (2010) 1106-1110
A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast
with nanoelectronics, which relies on "zero-current," gate-controlled operations. Efforts have been made to
control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these
effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to
demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching
ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a
low-power approach for spin-based information control.
Giant tunnel electroresistance with PbTiO3 ferroelectric tunnel
barriers
Auteurs : Crassous, A. Garcia, V. Karim Bouzehouane. Fusil, S. Vlooswijk, AHG. Rispens, G. Noheda, B.
Bibes, M. Barthelemy, A
The persistency of ferroelectricity in ultrathin films allows their use as tunnel barriers. Ferroelectric tunnel
junctions are used to explore the tunneling electroresistance effect-a change in the electrical resistance associated
with polarization reversal in the ferroelectric barrier layer-resulting from the interplay between ferroelectricity
and quantum-mechanical tunneling. Here, we use piezoresponse force microscopy and conductive-tip atomic
force microscopy at room temperature to demonstrate the resistive readout of the polarization state through its
influence on the tunnel current in PbTiO3 ultrathin ferroelectric films. The tunnel electroresistance reaches
values of 50 000% through a 3.6 nm PbTiO3 film.
Interface-induced room-temperature multiferroicity in BaTiO(3)
Auteurs : Valencia, S; Crassous, A; Bocher, L; Garcia, V; Moya, X; Cherifi, RO; Deranlot, C;
Bouzehouane, K; Fusil, S; Zobelli, A; Gloter, A; Mathur, ND; Gaupp, A; Abrudan, R; Radu, F;
Barthelemy, A; Bibes, M
Réf. : NATURE MATERIALS 10 (10): 753-758 10.1038/NMAT3098 OCT 2011
Multiferroic materials possess two or more ferroic orders but have not been exploited in devices owing to the
scarcity of room-temperature examples. Those that are ferromagnetic and ferroelectric have potential
applications in multi-state data storage if the ferroic orders switch independently, or in electric-field controlled
spintronics if the magnetoelectric coupling is strong. Future applications could also exploit toroidal moments and
optical effects that arise from the simultaneous breaking of time-reversal and space-inversion symmetries. Here,
we use soft X-ray resonant magnetic scattering and piezoresponse force microscopy to reveal that, at the
interface with Fe or Co, ultrathin films of the archetypal ferroelectric BaTiO(3) simultaneously possess a
magnetization and a polarization that are both spontaneous and hysteretic at room temperature. Ab initio
calculations of realistic interface structures provide insight into the origin of the induced moments and bring
support to this new approach for creating room-temperature multiferroics.
28/02/2013
46
PUBLICATIONS
PROJETS 2008
Restoration of bulk magnetic properties by strain engineering in
epitaxial CoFe(2)O(4) (001) ultrathin films
Auteurs : Matzen, S.; Moussy, J. -B.; Mattana, R.; Petroff, F.; Gatel, C.; Warot-Fonrose, B.; Cezar, J. C.;
Barbier, A.; Arrio, M. -A.; Sainctavit, Ph.
10.1063/1.3622307 Published: AUG 1 2011
Issue: 5
DOI:
We report on the significantly enhanced in-plane magnetic properties of CoFe(2)O(4) (001) ultrathin layers (5
nm) grown on MgAl(2)O(4) (001) in comparison to films deposited on MgO (001). The predicted inverse spinel
structure is confirmed by x-ray magnetic circular dichroism measurements and transmission electronic
microscopy studies reveal a significant in-plane compressive strain, responsible for the strong film anisotropy.
These results show that strain engineering can be used to tailor the magnetic properties of oxide ultrathin films.
A large compressive strain restores bulk magnetic properties for CoFe(2)O(4) films at tunnel barrier thicknesses.
(C) 2011 American Institute of Physics. [doi:10.1063/1.3622307]
Ultrathin oxide films and interfaces for electronics and spintronics
Auteurs : Bibes M , Javier Villegas , Agnès Barthélémy
Réf. : ADVANCES IN PHYSICS 60 (2011)
Oxides have become a key ingredient for new concepts of electronic devices. To a large extent, this is due to the
profusion of new physics and novel functionalities arising from ultrathin oxide films and at oxide interfaces. We
present here a perspective on selected topics within this vast field and focus on two main issues. The first part of
this review is dedicated to the use of ultrathin films of insulating oxides as barriers for tunnel junctions. In
addition to dielectric non-magnetic epitaxial barriers, which can produce tunneling magnetoresistances in excess
of a few hundred percent, we pay special attention to the possibility of exploiting the multifunctional character of
some oxides in order to realize 'active' tunnel barriers. In these, the conductance across the barrier is not only
controlled by the bias voltage and/or the electrodes magnetic state, but also depends on the barrier ferroic state.
Some examples include spin-filtering effects using ferro- and ferrimagnetic oxides, and the possibility of
realizing hysteretic, multi-state junctions using ferroelectric barriers. The second part of this review is devoted to
novel states appearing at oxide interfaces. Often completely different from those of the corresponding bulk
materials, they bring about novel functionalities to be exploited in spintronics and electronics architectures. We
review the main mechanisms responsible for these new properties (such as magnetic coupling, charge transfer
and proximity effects) and summarize some of the most paradigmatic phenomena. These include the formation
of high-mobility two-dimensional electron gases at the interface between insulators, the emergence of
superconductivity (or ferromagnetism) at the interface between non-superconducting (or non-ferromagnetic)
materials, the observation of magnetoelectric effects at magnetic/ferroelectric interfaces or the effects of the
interplay and competing interactions at all-oxide ferromagnetic/superconducting interfaces. Finally, we link up
the two reviewed research fields and emphasize that the tunneling geometry is particularly suited to probe novel
interface effects at oxide barrier/electrode interfaces. We close by giving some directions toward tunneling
devices exploiting novel oxide interfacial phenomena.
28/02/2013
47
PUBLICATIONS
PROJETS 2008
[2008-067T] CLEL
Porteur : Marie-Emmanuelle Couprie
Thème 6
Seed level requirement for improving the temporal coherence of a
Free-Electron Laser
Auteurs : Lambert, G. Hara, T. Labat, M. Tanikawa, T. Tanaka, Y. Yabashi, M. Garzella, D. Carre, B.
Marie-Emmanuelle Couprie
Réf. : EPL 88 (2009) 14001
The temporal coherence of Free-Electron Laser (FEL) sources, which exhibit, in the self-amplified spontaneousemission mode, spiking spectral and temporal distributions, can be drastically improved by seeding with an
external laser or high-order harmonics. Here, experiments at 160 nm put in evidence that the improvement of
spectral properties (and thus temporal coherence) of the FEL radiation takes place for a larger seed intensity than
the one required to overcome the shot noise. Copyright (C) EPLA, 2009
[2008-070T] LongWave
Porteur : Raffaele Colombelli
Thème 7
In Situ Generation of Surface Plasmon Polaritons Using a NearInfrared Laser Diode
Auteurs : Costantini, D.; Greusard, L.; Bousseksou, A.; Rungsawang, R.; Zhang, T. P.; Callard, S.;
Decobert, J.; Lelarge, F.; Duan, G. -H.; De Wilde, Y.; Colombelli, R.
Réf. : NANO LETTERS Volume: 12 Issue: 9 Pages: 4693-4697 DOI: 10.1021/nl302040e Published:
SEP 2012
We demonstrate a semiconductor laser-based approach which enables plasmonic active devices in the telecom
wavelength range. We show that optimized laser structures based on tensile-strained InGaAlAs quantum wells
coupled to integrated metallic patternings enable surface plasmon generation in an electrically driven compact
device. Experimental evidence of surface plasmon generation is obtained with the slit-doublet experiment in the
near-field, using near-field scanning optical microscopy measurements.
28/02/2013
48
PUBLICATIONS
PROJETS 2008
[2008-071T] PSYCHE
Porteur : Sophie Bouchoule
Axe C
Addition of Si-Containing Gases for Anisotropic Etching of III-V
Materials in Chlorine-Based Inductively Coupled Plasma
Auteurs : Lina Gatilova, Sophie Bouchoule, Gilles Patriarche, Stéphane Guilet
Réf. : JAPANESE JOURNAL OF APPLIED PHYSICS 50 (8): Part 2 SI 10.1143/JJAP.50.08JE02 AUG
2011
We discuss the possibility of obtaining high-aspect-ratio etching of InP materials in Cl(2)- and HBr-based
inductively coupled plasmas (ICP) with the addition of Si-containing gases (SiH(4) or SiCl(4)). A vertical and
smooth etching profile is demonstrated in SiCl(4)/H(2) plasma. The effect of adding of a small amount of SiH(4)
to a previously optimised Cl(2)/H(2) chemistry is presented, and new SiH(4)/Cl(2) and SiH(4)/HBr chemistries
are proposed. Ex-situ energy-dispersive X-ray spectroscopy coupled to transmission electron microscopy (EDXTEM) is used to analyze the composition of the thin passivation layer deposited on the etched sidewalls. We
show that it consists of a Si-rich silicon oxide (Si/O similar to 1) in Cl(2)/H(2)/SiH(4) chemistry, and is changed
to nano-crystalline (nc-) Si in SiH(4)/Cl(2) chemistry depending on the SiH(4) percentage. Moreover, we show
that deep anisotropic etching of InP independent of the electrode coverplate material can be obtained via a
SiO(x) passivation mechanism with the addition of Si-containing gases. (C) 2011 The Japan Society of Applied
Physics
High-aspect-ratio inductively coupled plasma etching of InP using
SiH4/Cl-2: Avoiding the effect of electrode coverplate material
Auteurs : Gatilova, L; Bouchoule, S; Guilet, S; Patriarche, G
Réf. : JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 29 (2)(2011) 020601
A new SiH4/Cl-2 chemistry is proposed for the high-aspect-ratio etching of InP-based heterostructures.
Anisotropic etching is obtained through the deposition of a SiOx passivation layer on the etched sidewalls. SiH4
has been chosen as a single precursor for both Si and H species that are necessary to promote the passivation
process. Previously developed Cl-2/H-2- or HBr-based chemistries for anisotropic etching of laser waveguides
or vertical microcavities require a silicon wafer below the InP samples in order to assist the passivation
mechanism. In contrast, the authors show that a SiOx passivation can be achieved and maintained almost
independent of the nature of the wafer surface when SiH4 is added. This is of practical importance for the
processing of III-V wafers having the same size as the electrode or for III-V heterogeneous integration when IIIV dies bonded onto a 200/300 mm diameter wafer have to be etched. Smooth, notch-free, anisotropic etching of
InGa(Al)As/InP heterostructures is demonstrated. Ex situ energy-dispersive x-ray spectroscopy coupled to a
transmission electron microscope is used to analyze the composition of the thin passivation layer deposited on
the sidewalls of etched features. The authors show that the passivation layer consists of a Si-rich silicon oxide
(Si/O similar to 1) in Cl-2/H-2/SiH4 chemistry and is changed to nanocrystalline Si in SiH4/Cl-2 chemistry
depending on the SiH4 concentration in the feed gas. An aspect ratio as high as 28 is obtained in the latter case.
(C) 2011 American Vacuum Society.
28/02/2013
49
PUBLICATIONS
PROJETS 2008
[2008-072T] POMS
Porteur : Patrick Davidson
Thème 3
A PGSE-NMR Study of Molecular Self-Diffusion in Lamellar Phases
Doped with Polyoxometalates
Auteurs : Poulos, AS. Constantin, D. Davidson, P. Imperor, M. Judeinstein, P. Pansu, B
Réf. : JOURNAL OF PHYSICAL CHEMISTRY B 114 (2010)
220-227
Using pulsed gradient spin-echo NMR, We studied molecular self-diffusion in aligned samples of a hybrid
lyotropic lamellar L-alpha, phase. This composite organic-inorganic material was obtained by doping the
lamellar phase of the nonionic surfactant Brij-30 With the [PW12O40](3-) polyoxometalate (PO M). Both water
and POM self-diffusion display a large anisotropy, as diffusion is severely restricted along the normal to the
bilayers. Water diffusion in planes parallel to the bilayers does not depend oil the POM concentration but
depends on the lamellar period, which is due to a variable Fraction of "bound" water molecules. POM diffusion
in the hybrid L-alpha phase is almost 2 orders of magnitude slower than in aqueous Solution. Moreover, it is not
at all affected by the thickness of the aqueous medium separating the bilayers. This proves that the POM
nanoparticles do not freely diffuse in the interbilayer aqueous space but adsorb onto the PEG brushes that cover
both sides of the surfactant bilayers.
Communications: Short-range dynamics of a nematic liquidcrystalline phase
Auteurs : Poulos, AS. Constantin, D. Davidson, P. Pansu, B. Freyssingeas, E. Madsen, A. Chaneac, C
Réf. : JOURNAL OF CHEMICAL PHYSICS 132 (2010) 091101
Using x-ray photon correlation spectroscopy, we studied the dynamics in the nematic phase of a nanorod
suspension. The collective diffusion coefficient in the plane perpendicular to the director varies sharply with the
wave vector. Combining the structure factor and the diffusion coefficient, we find that the hydrodynamic
function of the phase decreases by more than a factor of 10 when going from length scales comparable to the
interparticle distance toward larger values. Thus, the collective dynamics of the nematic phase experiences
strong and scale-dependent slowing down, in contrast with isotropic suspensions of slender rods or of spherical
particles.
Orientational Order of Colloidal Disk-Shaped Particles under ShearFlow Conditions: a Rheological-Small-Angle X-ray Scattering Study
Auteurs : Bihannic, I; Baravian, C; Duval, JFL; Paineau, E; Meneau, F; Levitz, P; de Silva, JP; Davidson,
P; Michot, LJ
Réf. : JOURNAL OF PHYSICAL CHEMISTRY B 114 (2010)
The structure of a colloidal dispersion consisting of anisometric natural clay particles (beidellite) was followed
under shear-flow conditions by small-angle X-ray scattering (SAXS) measurements in a Couette-type cell. It is
28/02/2013
50
PUBLICATIONS
PROJETS 2008
shown that in this shear-thinning dispersion an orientational order develops with increasing shear rate. By use of
two different geometrical configurations for SAXS measurements, corresponding to incident beam parallel and
perpendicular to flow velocity gradient (radial and tangential configurations, respectively), it is observed that
SAXS patterns are anisotropic in both geometries, meaning that particles tend to align along a preferred
orientation with their normal in velocity gradient direction, and further they partly rotate around flow
streamlines. Quantitative interpretation of these results is successfully achieved upon derivation of a probability
distribution function accounting for biaxial particle orientation. From this distribution and following geometrical
arguments, the viscosity of the suspension was calculated for each shear rate and found to correctly compare
with rheological measurements, thereby appropriately relating the anisotropy of the SAXS patterns to
macroscopic flow behavior of the suspension.
[2008-075T] Magnetic-Graphene
Porteur : Marc Goerbig
Thème 4
Spin-flip excitations, spin waves, and magnetoexcitons in graphene
Landau levels at integer filling factors
Auteurs : Roldan R ; Julien FuchsN ; Marc GoerbigO
82
(2010) 205418
We study collective electronic excitations in graphene in the integer quantum-Hall regime, concentrating mainly
on excitations with spin reversal such as spin-flip and spin-wave excitations. We show that these excitations are
correctly accounted for in the time-dependent Hartree-Fock and strong magnetic field approximations, in
contrast to spin-conserving (magnetoexciton) modes which involve a strong Landau-level mixing at nonzero
wave vectors. The collective excitations are discussed in view of prominent theorems, such as Kohn's and
Larmor's. Whereas the latter remains valid in graphene and yields insight into the understanding of spindependent modes, Kohn's theorem does not apply to relativistic electrons in graphene. We finally calculate the
exchange correction to the chemical potential in the weak magnetic field limit.
The magnetic field particle-hole excitation spectrum in doped
graphene and in a standard two-dimensional electron gas
Auteurs : Roldan, R. Marc Goerbig, O. Julien FuchsN
Réf. : SEMICONDUCTOR SCIENCE AND TECHNOLOGY 25 (2010) 034005
The particle-hole excitation spectrum for doped graphene is calculated from the dynamical polarizability. We
study the zero and finite magnetic field cases and compare them to the standard two-dimensional electron gas.
The effects of electron-electron interaction are included within the random-phase approximation. From the
obtained polarizability, we study the screening effects and the collective excitations (plasmon, magneto-excitons,
upper-hybrid mode and linear magneto-plasmons). We stress the differences with the usual 2DEG.
28/02/2013
51
PUBLICATIONS
PROJETS 2008
Theory of Bernstein modes in graphene
Auteurs : Roldan, R; Marc GoerbigO; Julien FuchsN
Réf. : PHYSICAL REVIEW B 83 (20): Art. No. 205406 MAY 17 2011
We present a theoretical description of Bernstein modes that arise as a result of the coupling between
plasmonlike collective excitations (upper-hybrid mode) and inter-Landau-level excitations, in graphene in a
perpendicular magnetic field. These modes, which are apparent as avoided level crossings in the spectral
function obtained in the random-phase approximation, are described to great accuracy in a phenomenological
model. Bernstein modes, which may be measured in inelastic light-scattering experiments or in
photoconductivity spectroscopy, are a manifestation of the Coulomb interaction between the electrons and may
be used for a high-precision measurement of the upper-hybrid mode at small nonzero wave vectors.
[2008-080T] GEOFLOW
Porteur : Frédéric Moisy
Thème 3
Viscous spreading of an inertial wave beam in a rotating fluid
Auteurs : Cortet, PP. Lamriben, C. Frédéric Moisy
Réf. : PHYSICS OF FLUIDS 22 (2010) 086603
We report experimental measurements of inertial waves generated by an oscillating cylinder in a rotating fluid.
The two-dimensional wave takes place in a stationary cross-shaped wavepacket. Velocity and vorticity fields in a
vertical plane normal to the wavemaker are measured by a corotating particle image velocimetry system. The
viscous spreading of the wave beam and the associated decay of the velocity and vorticity envelopes are
characterized. They are found in good agreement with the similarity solution of a linear viscous theory, derived
under a quasiparallel assumption similar to the classical analysis of Thomas and Stevenson ["A similarity
solution for viscous internal waves," J. Fluid Mech. 54, 495 (1972)] for internal waves. (C) 2010 American
Institute of Physics. [doi:10.1063/1.3483468]
Direct Measurements of Anisotropic Energy Transfers in a Rotating
Turbulence Experiment
Auteurs : Lamriben C, Cortet PP,Frédéric Moisy
Réf. : PHYSICAL REVIEW LETTERS 107 (2): 10.1103/PhysRevLett.107.024503
We investigate experimentally the influence of a background rotation on the energy transfers in decaying grid
turbulence. The anisotropic energy flux density F(r) = <delta u(delta u)(2)>, where delta u is the vector velocity
increment over separation r, is determined for the first time by using particle image velocimetry. We show that
rotation induces an anisotropy of the energy flux del.F, which leads to an anisotropy growth of the energy
distribution E(r) = <(delta u)(2)>, in agreement with the von Karman-Howarth-Monin equation. Surprisingly,
28/02/2013
52
PUBLICATIONS
PROJETS 2008
our results prove that this anisotropy growth is essentially driven by a nearly radial, but orientation-dependent,
energy flux density F(r).
Excitation of inertial modes in a closed grid turbulence experiment
under rotation
Auteurs : Lamriben, C; Cortet, PP; Frédéric Moisy; Maas, LRM
Réf. : PHYSICS OF FLUIDS 23 (2011) 015102
We report an experimental study of the decay of grid-generated turbulence in a confined geometry submitted to a
global rotation. Turbulence is generated by rapidly towing a grid in a parallelepipedic water tank. The velocity
fields of a large number of independent decays are measured in a vertical plane parallel to the rotation axis using
a corotating particle image velocimetry system. We first show that, when a "simple" grid is used, a significant
amount of the kinetic energy (typically 50%) is stored in a reproducible flow composed of resonant inertial
modes. The spatial structure of those inertial modes, extracted by band-pass filtering, is found compatible with
the numerical results of L. R. M. Maas [Fluid Dyn. Res. 33, 373 (2003)]. The possible coupling between these
modes and turbulence suggests that turbulence cannot be considered as freely decaying in this configuration. We
demonstrate however that these inertial modes may be significantly reduced (down to 15% of the total energy)
by adding a set of inner tanks attached to the grid. These results suggest that it is possible to produce an
effectively freely decaying rotating turbulence in a confined geometry. (c) 2011 American Institute of Physics.
CHEMO-hydrodynamic coupling between forced advection in
porous media and self-sustained chemical waves
Auteurs : Atis, S.; Saha, S.; Auradou, H.; Martin, J.; Rakotomalala, N.; Talon, L.; Salin, D.
Réf. : CHAOS Volume: 22 Issue: 3
SEP 2012
Article Number: 037108 DOI: 10.1063/1.4734489 Published:
Autocatalytic reaction fronts between two reacting species in the absence of fluid flow, propagate as solitary
waves. The coupling between autocatalytic reaction front and forced simple hydrodynamic flows leads to
stationary fronts whose velocity and shape depend on the underlying flow field. We address the issue of the
chemico-hydrodynamic coupling between forced advection in porous media and self-sustained chemical waves.
Towards that purpose, we perform experiments over a wide range of flow velocities with the well characterized
iodate arsenious acid and chlorite-tetrathionate autocatalytic reactions in transparent packed beads porous media.
The characteristics of these porous media such as their porosity, tortuosity, and hydrodynamics dispersion are
determined. In a pack of beads, the characteristic pore size and the velocity field correlation length are of the
order of the bead size. In order to address these two length scales separately, we perform lattice Boltzmann
numerical simulations in a stochastic porous medium, which takes into account the log-normal permeability
distribution and the spatial correlation of the permeability field. In both experiments and numerical simulations,
we observe stationary fronts propagating at a constant velocity with an almost constant front width. Experiments
without flow in packed bead porous media with different bead sizes show that the front propagation depends on
the tortuous nature of diffusion in the pore space. We observe microscopic effects when the pores are of the size
of the chemical front width. We address both supportive co-current and adverse flows with respect to the
direction of propagation of the chemical reaction. For supportive flows, experiments and simulations allow
observation of two flow regimes. For adverse flow, we observe upstream and downstream front motion as well
as static front behaviors over a wide range of flow rates. In order to understand better these observed static state
fronts, flow experiments around a single obstacle were used to delineate the range of steady state behavior. A
model using the "eikonal thin front limit" explains the observed steady states. (C) 2012 American Institute of
Physics. [http://dx.doi.org/10.1063/1.4734489]
28/02/2013
53
PUBLICATIONS
PROJETS 2008
Earth rotation prevents exact solid-body rotation of fluids in the
laboratory
Auteurs : Boisson, J.; Cebron, D.; Moisy, F.; Cortet, P. -P.
Réf. : EPL Volume: 98
Published: JUN 2012
Issue: 5
DOI: 10.1209/0295-5075/98/59002
We report direct evidence of a secondary flow excited by the Earth rotation in a water-filled spherical container
spinning at constant rotation rate. This so-called tilt-over flow essentially consists in a rotation around an axis
which is slightly tilted with respect to the rotation axis of the sphere. In the astrophysical context, it corresponds
to the flow in the liquid cores of planets forced by precession of the planet rotation axis, and it has been proposed
to contribute to the generation of planetary magnetic fields. We detect this weak secondary flow using a particle
image velocimetry system mounted in the rotating frame. This secondary flow consists in a weak rotation,
thousand times smaller than the sphere rotation, around a horizontal axis which is stationary in the laboratory
frame. Its amplitude and orientation are in quantitative agreement with the theory of the tilt-over flow excited by
precession. These results show that setting a fluid in a perfect solid-body rotation in a laboratory experiment is
impossible -unless by tilting the rotation axis of the experiment parallel to the Earth rotation axis. Copyright (C)
EPLA, 2012
Inertial waves and modes excited by the libration of a rotating cube
Auteurs : Boisson, Jean; Lamriben, Cyril; Maas, Leo R. M.; Cortet, Pierre-Philippe; Moisy, Frederic
Réf. : PHYSICS OF FLUIDS Volume: 24 Issue: 7
Published: JUL 2012
Article Number: 076602 DOI: 10.1063/1.4731802
We report experimental measurements of the flow in a cubic container submitted to a longitudinal libration, i.e.,
a rotation modulated in time. Velocity fields in a vertical and a horizontal plane are measured in the librating
frame using a corotating particle image velocimetry system. When the libration frequency sigma(0) is smaller
than twice the mean rotation rate, Omega(0), inertial waves can propagate in the interior of the fluid. At arbitrary
excitation frequencies sigma(0) < 2 Omega(0), the oscillating flow shows two contributions: (i) a basic flow
induced by the libration motion, and (ii) inertial wave beams propagating obliquely upward and downward from
the horizontal edges of the cube. In addition to these two contributions, inertial modes may also be excited at
some specific resonant frequencies. We characterize in particular the resonance of the mode of lowest order
compatible with the symmetries of the forcing, noted [2,1,+]. By comparing the measured flow fields to the
expected inviscid inertial modes computed numerically [L. R. M. Maas, "On the amphidromic structure of
inertial waves in rectangular parallelepiped," Fluid Dyn. Res. 33, 373 (2003)], we show that only a subset of
inertial modes, matching the symmetries of the forcing, can be excited by the libration. (C) 2012 American
Institute of Physics. [http://dx.doi.org/10.1063/1.4731802]
Relation between first arrival time and permeability in self-affine
fractures with areas in contact
Auteurs : Talon L.; Auradou H.; Hansen A.
Réf. : EPL Volume: 97
Published: MAR 2012
28/02/2013
Issue: 6 Article Number: 68009
DOI: 10.1209/0295-5075/97/68009
54
PUBLICATIONS
PROJETS 2008
We demonstrate that the first arrival times in dispersive processes in self-affine fractures are governed by the
same length scale characterizing the fractures as that which controls their permeability. In one-dimensional
channel flow this length scale is the aperture of the bottle neck, i.e., the region having the smallest aperture. In
two dimensions, the concept of a bottle neck is generalized to that of a minimal path normal to the flow. The
length scale is then the average aperture along this path. There is a linear relationship between the first arrival
time and this length scale, even when there is strong overlap between the fracture surfaces creating areas with
zero permeability. We express the first arrival time directly in terms of the permeability. Copyright (C) EPLA,
2012
Stokes flow paths separation and recirculation cells in X-junctions
of varying angle
Auteurs : Cachile M.; Talon L.; Gomba J. M.; et al.
Réf. : PHYSICS OF FLUIDS Volume: 24 Issue: 2 Article Number: 021704 DOI: 10.1063/1.3690100
Published: FEB 2012
Fluid and solute transfer in X-junctions between straight channels is shown to depend critically on the junction
angle alpha in the Stokes flow regime. Experimentally, water and a water-dye solution are injected at equal flow
rates in two facing channels of the junction. Planar laser induced fluorescence (PLIF) measurements show that
the largest part of each injected fluid "bounces back" preferentially into the outlet channel at the lowest angle to
the injection; this is opposite to the inertial case and requires a high curvature of the corresponding streamlines.
The proportion of this fluid in the other channel decreases from 50% at alpha = 90 degrees to 0% at a threshold
angle. These counterintuitive features reflect the minimization of energy dissipation for Stokes flows. Finite
elements numerical simulations of a 2D Stokes flow of equivalent geometry confirm these results and show that,
below the threshold angle alpha(c) = 33.8 degrees, recirculation cells are present in the center part of the junction
and separate the two injected flows of the two solutions. Reducing further alpha leads to the appearance of new
recirculation cells with lower flow velocities. (c) 2012 American Institute of Physics.
[http://dx.doi.org.gate4.inist.fr/10.1063/1.3690100]
[2008-082T] NonFermiSupra
Porteur : Marcelo Rozenberg
Thème 4
Hund's coupling and its key role in tuning multiorbital correlations
Auteurs : de' Medici, L
Réf. : PHYSICAL REVIEW B 83 (20): Art. No. 205112 MAY 17 2011 PRL (2011) 107, 256 401
It is shown how, in multiband materials, the Hund's coupling plays a crucial role in tuning the degree of
electronic correlation. While in half-filled systems it enhances the correlations, in all other cases it pushes the
boundary for the Mott transition at very high critical couplings. Moreover in weakly hybridized nondegenerate
systems the Hund's coupling plays the role of band decoupler, causing a change from a collective to an
individual band behavior, due to the freezing of orbital fluctuations. In this situation the physics is strongly
dependent on individual filling and electronic structure of each band, and orbital-selective Mott transitions (or
28/02/2013
55
PUBLICATIONS
PROJETS 2008
even a cascade of such transitions) are to be expected. More generally a heavy differentiation in the actual degree
of correlation of different bands arises and the system can show both weakly and strongly correlated electrons.
Janus-Faced Influence of Hund's Rule Coupling in Strongly
Correlated Materials
Auteurs : de' Medici Luca; Mravlje Jernej; Georges Antoine
Réf. : PHYSICAL REVIEW LETTERS Volume: 107
Issue: 25
10.1103/PhysRevLett.107.256401 Published: DEC 12 2011
DOI:
We show that in multiband metals the correlations are strongly affected by Hund's rule coupling, which
depending on the filling promotes metallic, insulating or bad-metallic behavior. The quasiparticle coherence and
the proximity to a Mott insulator are influenced distinctly and, away from single- and half-filling, in opposite
ways. A strongly correlated bad metal far from a Mott phase is found there. We propose a concise classification
of 3d and 4d transition-metal oxides within which the ubiquitous occurrence of strong correlations in Ru- and
Cr-based oxides, as well as the recently measured high Neel temperatures in Tc-based perovskites are naturally
explained.
Role of oxygen-oxygen hopping in the three-band copper-oxide
model: Quasiparticle weight, metal insulator and magnetic phase
boundaries, gap values, and optical conductivity
Auteurs : Wang, X; de' Medici, L; Millis, AJ
We investigate the effect of oxygen-oxygen hopping on the three-band copper-oxide model relevant to high-T-c
cuprates, finding that the physics is changed only slightly as the oxygen-oxygen hopping is varied. The location
of the metal-insulator phase boundary in the plane of interaction strength and charge-transfer energy shifts by
similar to 0.5 eV or less along the charge-transfer axis, the quasiparticle weight has approximately the same
magnitude and doping dependence, and the qualitative characteristics of the electron-doped and hole-doped sides
of the phase diagram do not change. The results confirm the identification of La2CuO4 as a material with an
intermediate correlation strength. However, the magnetic phase boundary as well as higher energy features of the
optical spectrum are found to depend on the magnitude of the oxygen-oxygen hopping. We compare our results
to previously published one-band and three-band model calculations.
Covalency, double-counting, and the metal-insulator phase diagram
in transition metal oxides
Auteurs : Wang, Xin; Han, M. J.; de' Medici, Luca; Park, Hyowon; Marianetti, C. A.; Millis, Andrew J.
Issue: 19
10.1103/PhysRevB.86.195136 Published: NOV 26 2012
DOI:
Dynamical mean field theory calculations are used to show that for late transition metal oxides a critical variable
for the Mott/charge-transfer transition is the number of d electrons, which is determined by charge transfer from
oxygen ions. Insulating behavior is found only for a narrow range of d occupancy, irrespective of the size of the
intra-d Coulomb repulsion. The result is useful in interpreting "density functional + U" and "density functional
plus dynamical mean field" methods in which additional correlations are applied to a specific set of orbitals and
28/02/2013
56
PUBLICATIONS
PROJETS 2008
an important role is played by the "double counting correction" which dictates the occupancy of these correlated
orbitals. General considerations are presented and are illustrated by calculations for two representative transition
metal oxide systems: layered perovskite Cu-based high-T-c materials, an orbitally nondegenerate electronically
quasi-two-dimensional system, and pseudocubic rare earch nickelates, an orbitally degenerate electronically
three-dimensional system. Density functional calculations yield d occupancies very far from the Mott metalinsulator phase boundary in the nickelate materials, but closer to it in the cuprates, indicating the sensitivity of
theoretical models of the cuprates to the choice of double counting correction, and corroborating the critical role
of lattice distortions in attaining the experimentally observed insulating phase in the nickelates.
Path to poor coherence in the periodic Anderson model from Mott
physics and hybridization
Auteurs : Amaricci A.; Medici L. De'; Sordi G.; et al.
Volume: 85
Issue: 23
10.1103/PhysRevB.85.235110 Published: JUN 5 2012
DOI:
We investigate the anomalous metal arising from hole-doping the Mott insulating state in the periodic Anderson
model. Using dynamical mean-field theory we show that, as opposed to the electron-doped case, in the holedoped regime the hybridization between localized and delocalized orbitals leads to the formation of composite
quasiparticles reminiscent of the Zhang-Rice singlets. We compute the coherence temperature of this state,
showing its extremely small value at low doping. As a consequence the weakly doped Mott state deviates from
the predictions of Fermi-liquid theory already at small temperatures. The onset of the Zhang-Rice state and of
the consequent poor coherence is due to the electronic structure in which both localized and itinerant carriers
have to be involved in the formation of the conduction states and to the proximity to the Mott state. By
investigating the magnetic properties of this state, we discuss the relation between the anomalous metallic
properties and the behavior of the magnetic degrees of freedom.
[2008-086T] XDIF
Porteur : Hamed Merdji
Thème 6
Single-shot Femtosecond X-Ray Holography Using Extended
References
Auteurs : Gauthier D, Guizar-Sicairos M, Ge X, Boutu W , Carre B, Fienup JR, Hamed Merdji
In the context of x-ray lensless imaging, we present a recent approach for Fourier transform holography based on
the use of extended references. Major advances shown here rely on a high signal efficiency and on the direct
image reconstruction of the object performed by a simple linear derivative. Moreover, the extended holographic
reference is easy to manufacture and can be applied to a variety of imaging experiments. Here we demonstrate
single-shot imaging with a table-top, laser-based coherent soft x-ray source. A spatial resolution of 110 nm was
obtained with an integration time of 20 fs.
28/02/2013
57
PUBLICATIONS
PROJETS 2008
[2008-088T] OPODRAG
Porteur : Fabien Bretenaker
Thème 7
Stimulated Raman scattering in an optical parametric oscillator
based on periodically poled MgO-doped stoichiometric LiTaO3
Auteurs : My TH, Robin O, Mhibik, O, Fabien Bretenhacker, C. Drag
Réf. : OPTICS EXPRESS 17 (2009) 5912-5918
The evolution of the spectrum of a singly resonant optical parametric oscillator based on an MgO-doped
periodically poled stoichiometric lithium tantalate crystal is observed when the pump power is varied. The onset
of cascade Raman lasing due to stimulated Raman scattering in the nonlinear crystal is analyzed. Spurious
frequency doubling and sum-frequency generation phenomena are observed and understood. A strong reduction
of the intracavity Raman scattering is obtained by a careful adjustment of the cavity losses. (C) 2009 Optical
Society of America
Frequency stabilization at the kilohertz level of a continuous
intracavity frequency-doubled singly resonant optical parametric
oscillator
Auteurs : Mhibik, O. My, TH. Paboeuf, D. Fabien Bretenaker. Drag, C
Réf. : OPTICS LETTERS 35 (2010) 2364-2366
A continuous intracavity frequency-doubled singly resonant optical parametric oscillator (OPO) is stabilized to
the side of the transmission peak of a medium finesse Fabry-Perot cavity. The narrow bandwidth of the
frequency noise of this OPO allows this simple scheme to lead to a stability of a few kilohertz with respect to the
locking etalon. The system, operating in the visible domain, remains locked for more than 1 h. (C) 2010 Optical
Society of America
Diode-pumped Pr:BaY(2)F(8) continuous-wave orange laser
Auteurs : D Paboeuf, O Mhibik, F Bretenaker,P Goldner, D Parisi, M Tonelli
Réf. : OPTICS LETTERS
Published: JAN 15 2011
Volume: 36
Issue: 2
Pages: 280-282
DOI: 10.1364/OL.36.000280
We report the realization of the continuous wave laser emission in the orange at 607 nm from a Pr: BaY(2)F(8)
(Pr:BYF) crystal pumped by a blue GaN laser diode. A maximal output power of 78 mW is obtained in a quasisingle transverse mode beam. The effect of reabsorption losses at the laser wavelength is also evidenced. (C)
2011 Optical Society of America.
28/02/2013
58
PUBLICATIONS
PROJETS 2008
Sub-kHz-level relative stabilization of an intracavity doubled
continuous wave optical parametric oscillator using Pound-DreverHall scheme
Auteurs : O Mhibik, D Paboeuf, C Drag, F Bretenaker
Réf. : OPTICS EXPRESS 19 (19): 18049-18057 SEP 12 2011
We report the relative frequency stabilization of an intracavity frequency doubled singly resonant optical
parametric oscillator on a Fabry-Perot etalon. The red/orange radiation produced by the frequency doubling of
the intracavity resonant idler is stabilized using the Pound-Drever-Hall locking technique. The relative frequency
noise of this orange light, when integrated from 1 Hz to 50 kHz, corresponds to a standard deviation of 700 Hz.
The frequency noise of the pump laser is shown experimentally to be transferred to the non resonant signal
beam.
Optimization of the resonant wave output coupling of a singly
resonant optical parametric oscillator using an intracavity plate
Auteurs : Paboeuf, D.; Mhibik, O.; Bretenaker, F.; Drag, C.
Réf. : APPLIED PHYSICS B-LASERS AND OPTICS Volume: 108
10.1007/s00340-012-4946-4 Published: AUG 2012
Issue: 2
Pages: 289-293
DOI:
We present a technique allowing us to optimize the output coupling of the resonant wave of a singly resonant
optical parametric oscillator (SRO). By inserting a silica plate inside the cavity and tilting it around the Brewster
angle, the output coupling of the SRO can be easily varied. This technique combines in principle the advantage
of an efficient output coupling together with the possibility of controlling the frequency of the resonant wave of
the SRO. We use this plate inside a 532-nm-pumped SRO to extract 1.6 W at 1.2 mu m with a pump depletion of
80 %. We also show the possibility of determining the intracavity loss of the OPO, which is a useful parameter
regarding its optimization.
Ultranarrow resonance due to coherent population oscillations in a
Lambda-type atomic system
Auteurs : Laupretre T.; Kumar S.; Berger P.; et al.
Réf. : PHYSICAL REVIEW A
Volume: 85
Issue: 5
10.1103/PhysRevA.85.051805 Published: MAY 24 2012
DOI:
It is well known that ultranarrow electromagnetically induced transparency (EIT) resonances can be observed in
atomic gases at room temperature. We report here the experimental observation of another type of ultranarrow
resonance, as narrow as the EIT ones, in a Lambda system selected by light polarization in metastable He-4 at
room temperature. It is shown to be due to coherent population oscillations in an open two-level system (TLS).
For perpendicular linearly polarized coupling and probe beams, this system can be considered as two coupled
open TLSs, in which the ground-state populations exhibit antiphase oscillations. We also predict theoretically
that in the case of two parallel polarizations, the system would behave like a closed TLS, and the narrow
resonance associated with these oscillations would disappear.
28/02/2013
59
PUBLICATIONS
PROJETS 2008
[2008-091T] CAAS
Porteur : P. Voisin
Axe B
Anisotropic magneto-resistance in a GaMnAs-based single impurity
tunnel diode: A tight binding approach
Auteurs : Nestoklon, MO; Krebs, O; Jaffres, H; Ruttala, S; George, JM; Jancu, JM; Voisin, P
Réf. : APPLIED PHYSICS LETTERS, 100 (6):10.1063/1.3683525 FEB 6 2012
Using an advanced tight-binding approach, we estimate the anisotropy of the tunnel transmission associated with
the rotation of the 5/2 spin of a single Mn atom forming an acceptor state in GaAs and located near an AlGaAs
tunnel barrier. Significant anisotropies in both in-plane and out-of-plane geometries are found, resulting from the
combination of the large spin-orbit coupling associated with the p-d exchange interaction, cubic anisotropy of
heavy-hole dispersion and the low C-2v symmetry of the chemical bonds. (C) 2012 American Institute of
Physics. [doi: 10.1063/1.3683525]
Spin splitting of electron states in (110) quantum wells: Symmetry
analysis and k.p theory versus microscopic calculations
Auteurs : Nestoklon M. O.; Tarasenko S. A.; Jancu J. -M.; et al.
Volume: 85
Issue: 20
10.1103/PhysRevB.85.205307 Published: MAY 9 2012
DOI:
Spin splittings in quantum wells have attracted considerable attention over the past decade due to potential
application of semiconductor spin properties to "spintronic devices." Recent experimental results stimulate
theoretical investigations of new physical situations like unconventional growth directions. Here we focus on
electron spin properties in (110)-oriented quantum wells that are of particular interest because qualitative
symmetry analysis shows that spin relaxation by the D'yakonov-Perel' mechanism should be strongly suppressed
in this geometry. We combine symmetry analysis, envelope function theory, and tight-binding calculation and
obtain quantitative description of the in-plane wave vector, well width, and applied electric field dependence of
the spin structure of electron subbands in (110) quantum wells.
28/02/2013
60
PUBLICATIONS
PROJETS 2008
[2008-091T] CAAS 1 & [2012-019T] CAAS 2
Porteur : P. Voisin
Axe B
Anomalous suppression of valley splittings in lead salt nanocrystals
without inversion center
Auteurs : Poddubny, A. N.; Nestoklon, M. O.; Goupalov, S. V.
Issue: 3
10.1103/PhysRevB.86.035324 Published: JUL 25 2012
DOI:
We demonstrate that confinement-induced intervalley splittings of electron energy levels in PbSe and PbS
nanocrystals are sensitive to the arrangement of atoms within a nanocrystal. The splittings are strongly
suppressed for stoichiometric nanocrystals of T-d point symmetry lacking a center of inversion as opposed to
nonstoichiometric nanocrystals of O-h point symmetry having an inversion center. Our findings are supported by
both atomistic sp(3)d(5)s* tight-binding calculations and a symmetry analysis.
[2008-092T] ALVAREZ
Porteur : Tiberiu Minea
Axe C
Nanostructured tantalum nitride films as buffer-layer for carbon
nanotube growth
Auteurs : Jin C, Delmas M, Aubert P, Alvarez F, Minea T, Hugon MC, Bouchet-Fabre, B
Réf. : THIN SOLID FILMS 519 (12): 4097-4100 Sp. Iss. SI APR 1
Tantalum nitride (TaNx) films are usually used as barriers to the diffusion of copper in the substrate for
electronic devices. In the present work, the TaNx coating plays an extra role in the iron catalyzed chemical vapor
deposition production of carbon nanotubes (CNT). The CNTs were grown at 850 degrees C on TaNx films
prepared by radio frequency magnetron sputtering. The correlation between the CNT morphology and growth
rate, and the pristine TaNx film nature, is investigated by comparing the evolution of the nano-composition,
roughness and nano-crystallinity of the TaNx films both after annealing and CVD at 850 degrees C. 2011
Published by Elsevier B.V.
28/02/2013
61
PUBLICATIONS
PROJETS 2008
[2008-095T] STP
Porteur : Nita Dragoe
Axe C
Electrical transport properties of Mn-doped LaFeAsO oxypnictide
Auteurs : Berardan, D. Loreynne Loreynne Pinsard-Gaudart. Nita Dragoe
Réf. : JOURNAL OF ALLOYS AND COMPOUNDS 481 (2009) 470-472
We report on the electrical transport properties of the Mn-doped LaFe1-xMnxAsO oxypnictide system. We show
that the substitution of iron by manganese in the FeAs layer leads to a gradual expansion of the lattice parameters
and of the Fe-As and Fe-Fe bond lengths, as well as a change in the angles of the FeAs4 tetrahedron which
becomes more regular. The structural transition from tetragonal to orthorhombic coupled to the emergence of a
spin density wave is rapidly suppressed by Mn doping. Interestingly, Mn doping does not lead to p-type
behaviour. Moreover, no superconducting transition is observed, and the system evidences a metalsemiconductor transition around x = 0.03. Thus, there is apparently no symmetric behaviour of the manganese
doping and cobalt doping in the FeAs layer of the LaFeAsO system. (C) 2009 Elsevier B.V. All rights reserved.
Bi1-xSrxCuSeO oxyselenides as promising thermoelectric materials
Auteurs : Zhao, LD. Berardan, D. Pei, YL. Byl, C. Loreynne Loreynne Pinsard-Gaudart. Nita Dragoe
p-type BiCuSeO, a layered oxyselenide composed of conductive (Cu2Se2)(2-) layers alternately stacked with
insulating (Bi2O2)(2+) layers, shows an enhancement of the electrical conductivity after substituting Bi3+ by
Sr2+, from 470 S m(-1) (BiCuSeO) to 4.8 x 10(4) S m(-1) (Bi0.85Sr0.15CuSeO) at 293 K. Coupled to high
Seebeck coefficients, this leads to promising values of the thermoelectric power factor that exceeds 500 mu W
m(-1) K-2 at 873 K. Moreover, the thermal conductivity of these layered compounds is lower than 1 W m(-1) K1 at 873 K. Maximum ZT values reach 0.76 at 873 K, making this family promising for thermoelectric
applications in the medium temperature range. (C) 2010 American Institute of Physics. [doi:10.1063/1.3485050]
Effects of Co doping on the transport properties and
superconductivity in CeFe1-xCoxAsO
Auteurs : Zhao, LD. Berardan, D. Byl, C. Loreynne Loreynne Pinsard-Gaudart. Nita Dragoe
Réf. : JOURNAL OF PHYSICS-CONDENSED MATTER 22 (2010) 115701
A series of CeFe1-xCoxAsO oxyarsenide compounds with Co doping on iron sites (x = 0-0.2) have been
synthesized by a solid state reaction method. The effects of Co doping on the electrical transport properties and
superconductivity were analyzed with a special emphasis on the analysis of thermopower. Undoped CeFeAsO
shows an electrical resistivity anomaly at about 150 K, which was ascribed to a spin-density-wave (SDW)
instability. This anomaly is suppressed and a superconducting transition occurs at T-c = 3.2 K in
CeFe0.95Co0.05AsO, the maximum superconducting transition temperature (T-c) of 12.5 K is observed in
CeFe0.90Co0.10AsO, and the thermopower is increased by the Co doping. As has been previously suggested,
28/02/2013
62
PUBLICATIONS
PROJETS 2008
the emergence of superconductivity seems to be closely linked to the thermopower, and there is a close
correlation between Tc and the thermopower, both showing a similar dome-like doping dependence.
Electrical transport properties of F-doped LaFeAsO oxypnictide
Auteurs : Zhao LD ; Berardan D ; Nita Dragoe
Réf. : JOURNAL OF ALLOYS AND COMPOUNDS 508 (2010) 606-609
We demonstrate an all-silicon photodetector working at telecom wavelength. The device is a simple metalsemiconductor-metal detector fabricated on silicon-on-insulator. A two-dimensional photonic crystal nanocavity
(Q = 60,000) is used to increase the response that arises from the linear and two-photon absorption of silicon.
The responsivity of the detector is about 20 mA/W and its bandwidth is larger than 1 GHz. (C) 2010 Optical
Society of America
Electronic phase diagram of NdFe1-xRhxAsO
Auteurs : Berardan, D. Zhao, LD. Loreynne Loreynne Pinsard-Gaudart. Nita Dragoe
81 (2010)
094506
We report on the electrical resistivity, thermoelectric power, and electronic phase diagram of rhodium-doped
NdFeAsO. Rhodium doping suppresses the structural phase transition and spin-density wave observed in the
undoped material, and superconductivity emerges at x close to 0.05, despite the distortion of FeAs4 tetrahedra
induced by the large size difference between Rh and Fe elements. The T-c (x) curve is domelike, and the highest
T-c is reached at x=0.1, with T-c(onset)= 18 K. An upturn of the electrical resistivity above T-c has been
observed, with a Kondo-type behavior above T-c and a Fermi- liquid behavior close to room temperature.
Superconductivity at 15 K in NdFe0.9Rh0.1AsO without F-doping
Auteurs : Berardan, D. Zhao, LD. Loreynne Loreynne Pinsard-Gaudart. Nita Dragoe
Réf. : PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 (2010) 165-167
We present results of transport and magnetic properties measurements performed on polycrystalline
NdFe0.9Rh0.1AsO. Despite the large size difference between Fe and Rh elements, this compound undergoes a
superconducting transition with T-c similar to 15 K. We have compared the transport properties of this Rh-doped
oxypnictide with that of optimally doped NdFeAsO0.88F0.12 Contrary to this latter compound, a strong upturn
of the normal-state resistivity occurs above T-c, and no peak of the thermopower has been observed. (C) 2009
Elsevier B.V. All rights reserved.
28/02/2013
63

Sommaire - Triangle de la Physique

Transcription

Documents pareils

Offres de technologies - CCI Champagne

DT-3BANDS XL - Delair-Tech

sport-elec - Sporttema

Management-of-infertile-women-of-old-age-with

OSC/9213 CATA SONGBOOKS 03 x

Summer Reading Program Grades 4 and 5

The Evolving Field of Laser Surgery

Endometriosis-cyst-ethanol-sclerosis-after-ultrasound

Peut-on utiliser la crème Vaniqa sur les seins en parallèle d`une

Fractional Treatment of Aging Skin with an

isros 2009 - CCT

50% off Photorejuvenation/ IPL