Catégorie : Collaborations

Abstract : Transformations of cooperative electronic states by impacts of optical pumping or/and electrostatic doping is a new mainstream in physics of correlated systems. Here we present a semi-phenomenological modelling of spacio-temporal effects in a system where the light absorption goes through a channel creating the excitons – intra-molecular ones or bound electron-hole pairs -and finally the condensate of optical excitons feeds and stimulates phase transformations. Interacting with a near-critical order parameter and deformations, the excitons are subject to self-trapping. That locally enhances their density which can surpass a critical value to trigger the phase transformation, even if the mean density is below the required threshold. The model can be used e.g. as a simplified version of optically induced neutral-ionic transitions in organic chain compounds.

1 LPTMS – Laboratoire de Physique Théorique et Modèles Statistiques
2 LPS – Laboratoire de Physique des Solides

Abstract : Motivated by the intriguing phase behavior of charged colloidal platelets, we investigate the structure and dynamics of charged repulsive disks by means of Monte-Carlo simulations. The electrostatic interactions are taken into account through an effective two-body potential, obtained within the non-linear Poisson-Boltzmann formalism, which has the form of anisotropic screened Coulomb potential. Recently, we showed that the original intrinsic anisotropy of the electrostatic potential in competition with excluded volume effects leads to a rich phase behavior that not only includes various liquid-crsytalline phases but also predicts the existence of novel structures composed of alternating nematic-antinematic sheets. Here, we examine the structural and dynamical signatures of each of the observed structures for both translational and rotational degrees of freedom. Finally, we discuss the influence of effective charge value and our results in relation to experimental findings on charged platelet suspensions.

Auteurs

Sara Jabbari-Farouji 1, 2 Jean-Jacques Weis 3 Patrick Davidson 4 Pierre Levitz 5 Emmanuel Trizac 2
1 LIPhy – Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]
2 LPTMS – Laboratoire de Physique Théorique et Modèles Statistiques
3 Laboratoire de Physique Théorique
4 LPS – Laboratoire de Physique des Solides
5 PECSA – Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques

Abstract : The effects of particle correlations on the spectral broadening due to the radiator motion (Doppler broadening) are discussed for a Ni-like XUV laser line pumped in two different regimes of collisional excitation. The transient pumping for which ionic temperature is relatively low (the plasma coupling parameters is large), and the quasi steady-state pumping (QSS) for which the ionic temperature is higher and the plasma coupling parameter of the order of 1 are considered. It is shown by using classical Molecular Dynamics simulation techniques that in both cases the effect of correlations modify the radiator-motion broadened profiles and cannot be neglected in evaluating Doppler effect. This is due to the fact that the radiator velocity changes during the radiation emission resulting in a mixing of velocities in the line profile. It is also shown that this results in a homogenization of the intrinsic line profiles.

Annette Calisti 1 Sandrine Ferri 1 Caroline Mossé 1 Bernard Talin 1 Annie Klisnick 2 Limin Meng 2 Djamel Benredjem 3 Olivier Guilbaud 4
1 PIIM – Physique des interactions ioniques et moléculaires
2 ISMO – Institut des Sciences Moléculaires d’Orsay
3 LAC – Laboratoire Aimé Cotton
4 LPGP – Laboratoire de physique des gaz et des plasmas

Richard Legras 1 Yohann Benard 2
1 LuMIn – Laboratoire Lumière, Matière et Interfaces
2 LAC – Laboratoire Aimé Cotton

Richard Legras 1 Yohann Benard 2
1 LuMIn – Laboratoire Lumière, Matière et Interfaces
2 LAC – Laboratoire Aimé Cotton

Guillaume Clavé 1 Géraud Delport 2 Cyrielle Roquelet 2 Jean‐sébastien Lauret 2 Emmanuelle Deleporte 2 Benjamin Langlois 3 Fabien Vialla 3 Romain Parret 3 Christophe Voisin 3 Philippe Roussignol 3 Bruno Jousselme 4 Alexandre Gloter 5 Odile Stephan 5 Arianna Filoramo 1 Vincent Derycke 1 Stéphane Campidelli 1
1 LISO – Laboratoire Interfaces et Surfaces d’Oxydes
SPEC – UMR3680 – Service de physique de l’état condensé, IRAMIS – Institut Rayonnement Matière de Saclay
2 LAC – Laboratoire Aimé Cotton
3 LPA – Laboratoire Pierre Aigrain
4 LCSI – Laboratoire de Chimie des Surfaces et Interfaces
5 LPS – Laboratoire de Physique des Solides

François Boulogne 1 F. Giorgiutti-Dauphiné L. Pauchard 2
1 LPS – Laboratoire de Physique des Solides
2 FAST – Fluides, automatique, systèmes thermiques

François Boulogne 1 F. Giorgiutti-Dauphiné L. Pauchard 2
1 LPS – Laboratoire de Physique des Solides
2 FAST – Fluides, automatique, systèmes thermiques

François Boulogne 1 L. Pauchard 2 F. Giorgiutti-Dauphiné
1 LPS – Laboratoire de Physique des Solides
2 FAST – Fluides, automatique, systèmes thermiques

François Boulogne 1 M. Fardin S. Lerouge 2 L. Pauchard 3 F. Giorgiutti-Dauphiné
1 LPS – Laboratoire de Physique des Solides
2 MSC (UMR_7057) – Matière et Systèmes Complexes
3 FAST – Fluides, automatique, systèmes thermiques