Laboratoire Charles Coulomb UMR 5221 CNRS-UM2 (L2C)

Congress/Workshop from 2013-05-27 to 2013-05-31: EMRS SYMPOSIUM Group III Nitrides

2013-05-27

Congress/Workshop from 2013-06-10 to 2013-06-14: Ecole d'Initiation à la Spectroscopie d'Absorption X

2013-06-10

Congress/Workshop from 2013-06-23 to 2013-06-28: Summer school of the physics and applications of nitrides

2013-06-23

Seminar: TBA

(URBANO|supprimer_tags|texte_backend) Alfredo — 2013-05-23T12:00:00Z

Seminar: Dynamics in highly frustrated magnets : from resonating states to glassiness

(CEPAS|supprimer_tags|texte_backend) Olivier — 2013-05-24T12:00:00Z

Geometrically frustrated magnets may have an interesting variety of competing ground states, such as antiferromagnetic broken-symmetry states, spin-liquid states (which do not break any symmetry), or "frozen" states. A typical example is the Heisenberg model on the 2d Kagome lattice, for which the frustration leads to an exponential number of degenerate ground states. The standard large-S theory describes spin-wave excitations about a single broken-symmetry state (Goldstone mode) and therefore, breaks down in this context: one has to describe the dynamics within the low-energy landscape. This dynamics is special in that it involves collective rearrangements of spins which must respect some local constraints. I will discuss two effects: (i) the lifting of the degeneracy induced by the zero-point motion within the low-energy landscape: a given ground state is selected; it is the most "flexible", has long range order but is still "resonating". (ii) the loss of ergodicity of the dynamics below a crossover temperature: the dynamics becomes heterogeneous in space and the system develops some locally frozen disorder. The phase-space is then broken into many pockets, as in a glass.

Seminar: Angular manipulation and dynamics at the single-molecule level

(PEDACI|supprimer_tags|texte_backend) Francesco — 2013-05-24T12:00:00Z

The possibility to directly manipulate microscopic objects with focused laser beams has opened many new possibilities in biophysics. Using microscopic handles, optical tweezers allow to apply and measure forces directly to single molecules, probing mechanical properties of DNA, RNA or protein motors, with nanometer and pico Newton resolution. The Optical Torque Wrench is an extension of optical tweezers towards the control and measurement of angle and torque of nano-fabricated particles. It has the potential to unravel new and fast dynamical processes in biological systems where rotation and torque are relevant. Examples include the coiling of the DNA double helix, or the fast spinning of flagella in bacteria. I will describe the optical technique and show how the angular dynamics of the trapped particle is a nice and simple example of excitability, a dynamic property found in different other non-linear systems. I will also discuss preliminary results which show the potential of the technique in manipulating and measuring the torque generated by a single bacterial flagellar motor, a powerful nano-scale biological rotary motor.

(ART_ACL) Exciton decay through plasmon modes in planar metal-semiconductor structures

2013-05-15T22:00:00Z

We develop a nonlocal dielectric-response theory to describe the temperature dependence of exciton lifetime in metal-semiconductor heterostructures. Coupling between excitons and surface plasmons results in a strongly nonmonotonous behavior of exciton decay rate versus temperature, affected by surface plasmons on both sides of the metal layer. Unlike the photons, surface plasmons are not able to escape the sample; hence, the additional decay channel for excitons appears solely due to the plasmon scattering in metal and metal-dielectric interfaces. Tuning the plasmon frequency, one can control the exciton lifetime and under certain conditions emission efficiency

(ART_ACL) Nonequilibrium glass transitions in driven and active matter

2013-05-15T22:00:00Z

The glass transition, extensively studied in dense fluids, polymers, or colloids, corresponds to a dramatic evolution of equilibrium transport coefficients upon a modest change of control parameter, like temperature or pressure. A similar phenomenology is found in many systems evolving far from equilibrium, such as driven granular media, active and living matter. While many theories compete to describe the glass transition at thermal equilibrium, very little is understood far from equilibrium. Here, we solve the dynamics of a specific, yet representative, class of glass models in the presence of nonthermal driving forces and energy dissipation, and show that a dynamic arrest can take place in these nonequilibrium conditions. While the location of the transition depends on the specifics of the driving mechanisms, important features of the glassy dynamics are insensitive to details, suggesting that an 'effective' thermal dynamics generically emerges at long time scales in nonequilibrium systems close to dynamic arrest.

MIRO and all that

Dominique CARON — 2013-04-23T16:32:39Z

Le Laboratoire Charles Coulomb et l'Université Montpellier II ont le plaisir d'accueillir le Workshop “MIRO and all that” (MIRO 2013). Ce passionnant événement réunissant les meilleurs chercheurs mondiaux dans le domaine se tiendra du 13 au 16 Mai 2013 dans les locaux du Laboratoire Charles Coulomb à l'Université Montpellier II. Le phénomène de « Microwave Induced Resistance Oscillations » (MIRO) a été découvert par M. Zudov et RR. Du en 1997. Il s'agit de très fortes oscillations de la (...) - 30. Conférences et colloques

Distinction pour Wojciech Knap

Sébastien LAYSSAC — 2013-03-15T14:45:58Z

Wojciech Knap, Directeur de Recherche CNRS, au Laboratoire Charles Coulomb, a reçu le titre honorifique de Professeur de la part du président de la République de Pologne, lors d'une cérémonie qui s'est déroulée au palais présidentiel le 14 février 2013.

- Actualités

Ecole d'Initiation à la Diffusion Raman pour l'Etude des Nanostructures à base de Carbone

Dominique CARON — 2013-03-14T16:15:47Z

Du 1 au 5 juillet 2013 L'Ecole d'Initiation à la Diffusion Raman pour l'Etude des Nanostructures à base de Carbone a pour but de donner les bases théoriques et méthodologiques de la diffusion Raman pour l'étude des nanostructures à base de carbone. La spécificité de cette formation est de coupler des cours théoriques et des travaux pratiques de diffusion Raman appliqués aux nanostructures à base de carbone. Cette session pourra accueillir un maximum de 24 personnes (chercheurs, ingénieurs et (...) - 30. Conférences et colloques