Catégorie : Collaborations

Abstract : A comparative study of the vibrational properties of W(CO)6 has been performed in different solids at cryogenic temperatures focusing on the IR absorption and the vibrational dynamics of the CO stretching mode of the organometallic compound. Guest-host interactions areinvestigated in doped solids through the linear IR spectroscopy and four-wave mixing techniques at different temperatures. We show how the host nature, the trapping site, the crystallographic ordering affect the properties of the guest molecule and in particular its vibrational dynamics.

Raphaël Thon 1 Wutharath Chin 1 Didier Chamma 1 Alejandro Gutiérrez Quintanilla 1 Michele Chevalier 1 Jean-Pierre Galaup 2 Claudine Crépin 3, 1
1 ISMO – Institut des Sciences Moléculaires d’Orsay
2 LAC – Laboratoire Aimé Cotton
3 SYSIPHE
ISMO – Institut des Sciences Moléculaires d’Orsay

Richard Legras 1 David Rio 2
1 LuMIn – Laboratoire Lumière, Matière et Interfaces
2 LAC – Laboratoire Aimé Cotton

Abstract : Bacterial biofilms correspond to surface-associated bacterial communities embedded in hydrogel-like matrix, in which high cell density, reduced diffusion and physico-chemical heterogeneity play a protective role and induce novel behaviors. In this review, we present recent advances on the understanding of how bacterial mechanical properties, from single cell to high-cell density community, determine biofilm tri-dimensional growth and eventual dispersion and we attempt to draw a parallel between these properties and the mechanical properties of other well-studied hydrogels and living systems.

Catherine Even 1 Christian Marlière 2 Jean-Marc Ghigo 3 Jean-Marc Allain 4 Alba Marcellan 5 Eric Raspaud 1
1 LPS – Laboratoire de Physique des Solides
2 ISMO – Institut des Sciences Moléculaires d’Orsay
3 Génétique des Biofilms
4 M3DISIM – Mathematical and Mechanical Modeling with Data Interaction in Simulations for Medicine
LMS – Laboratoire de mécanique des solides, Inria Saclay – Ile de France
5 SIMM – Sciences et Ingénierie de la Matière Molle

Abstract : We measure the surface of CH33 NH33 PbI33 single crystals by making use of two photon photoemission spectroscopy. Our method monitors the electronic distribution of photoexcited electrons, explicitly discriminating the initial thermalization from slower dynamical processes. The reported results disclose the fast dissipation channels of hot carriers (0.25 ps), set a upper bound to the surface induced recombination velocity (< 4000 cm/s) and reveal the dramatic effect of shallow traps on the electrons dynamics. The picosecond localization of excited electrons in degraded CH33 NH33 PbI33 samples is consistent with the progressive reduction of photoconversion efficiency in operating devices. Minimizing the density of shallow traps and solving the aging problem may boost the macroscopic efficiency of solar cells to the theoretical limit.

Zhesheng Chen 1 Min-I Lee 2 Zailan Zhang 3 Hiba Diab 4 Damien Garrot 5 Ferdinand Lédée 4, 6 Pierre Fertey 7 Evangelos Papalazarou 2 Marino Marsi 2 Carlito Ponseca 8 Emmanuelle Deleporte 4, 6 Antonio Tejeda 2 Luca Perfetti 1
1 LSI – Laboratoire des Solides Irradiés
2 LPS – Laboratoire de Physique des Solides
3 IMPMC – Institut de minéralogie, de physique des matériaux et de cosmochimie
4 LAC – Laboratoire Aimé Cotton
5 GEMAC – Groupe d’Etude de la Matière Condensée
6 PPSM – Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires
7 SSOLEIL – Synchrotron SOLEIL
8 Lund University [Lund]

T. Chevalier 1 A. Dubey 1 S. Atis 1 A. Rosso 2 D. Salin 1 L. Talon 1
1 FAST – Fluides, automatique, systèmes thermiques
2 LPTMS – Laboratoire de Physique Théorique et Modèles Statistiques

David Rio 1 Kelly Woog 1 Richard Legras 2
1 LAC – Laboratoire Aimé Cotton
2 LuMIn – Laboratoire Lumière, Matière et Interfaces

Abstract : Hybrid perovskite thin films have demonstrated impressive performance for solar energy conversion and optoelectronic applications. However, further progress will benefit from a better knowledge of the intrinsic photophysics of materials. Here, the temperature-dependent emission properties of CH3NH3PbI3 single crystals are investigated and compared to those of thin polycrystalline films by means of steady-state and time-resolved photoluminescence spectroscopy. Single crystals photoluminescence present a sharp excitonic emission at high energy, with full width at half maximum of only 5 meV, assigned to free excitonic recombination. We highlight a strong thermal broadening of the free excitonic emission, due to exciton–LO-phonon coupling. The emission turned to be very short-lived with a subnanosecond dynamics, mainly induced by the fast trapping of the excitons. The free excitonic emission is completely absent of the thin film spectra, which are dominated by trap state bands.

Hiba Diab 1 Gaelle Trippe-Allard 1 Ferdinand Lédée 1 Khaoula Jemli 2 Christèle Vilar 3 Guillaume Bouchez 3 Vincent L.R Jacques 4 Antonio Tejeda 4 Jacky Even 5 Jean‐sébastien Lauret 6, * Emmanuelle Deleporte 6, * Damien Garrot 6, *
* Auteur correspondant
1 LAC – Laboratoire Aimé Cotton
2 PPSM – Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires
3 GEMAC – Groupe d’Etude de la Matière Condensée
4 LPS – Laboratoire de Physique des Solides
5 FOTON – Fonctions Optiques pour les Technologies de l’informatiON
6 LPQM – Laboratoire de Photonique Quantique et Moléculaire

Abstract : Fluids loaded with motile bacteria enter in the category of active matter, a new field currently developing at the convergence of biology, hydrodynamics and statistical physics. Such suspensions were shown recently to exhibit singular hydrodynamic transport properties. In this paper we review some recent results, either theoretical or experimental , on the active fluid rheology. We focus principally on bacteria suspensions and the objective is to provide the basis for understanding the emergence of the singular constitutive relations characterizing the macroscopic transport properties of such an active fluid under flow.

Eric Clement 1, * Anke Lindner 1 Carine Douarche 2 Harold Auradou 3
* Auteur correspondant
1 PMMH – Physique et mécanique des milieux hétérogenes (UMR 7636)
2 LPS – Laboratoire de Physique des Solides
3 FAST – Fluides, automatique, systèmes thermiques

Abstract : We consider a dynamical phase transition induced by a short optical pulse in a system prone to thermodynamical instability. We address the case of pumping to excitons whose density contributes directly to the order parameter. To describe both thermodynamic and dynamic effects on equal footing, we adopt a view of the excitonic insulator for the phase transition and suggest a formation of the Bose condensate for the pumped excitons. The work is motivated by experiments in donor-acceptor organic compounds with a neutral-ionic phase transition coupled to the spontaneous lattice dimerization and to charge transfer excitons. The double nature of the ensemble of excitons leads to an intricate time evolution, in particular to macroscopic quantum oscillations from the interference between the Bose condensate of excitons and the ground state of the excitonic insulator. The coupling of excitons and the order parameter also leads to self-trapping of their wave function, akin to self-focusing in optics. The locally enhanced density of excitons can surpass a critical value to trigger the phase transformation, even if the mean density is below the required threshold. The system is stratified in domains that evolve through dynamical phase transitions and sequences of merging.

Serguei Brazovskii 1 Natasha Kirova 2
1 LPTMS – Laboratoire de Physique Théorique et Modèles Statistiques
2 LPS – Laboratoire de Physique des Solides