Seminars coming up

[CM]

Seminar on   Disorder and strong electron correlations




Friday, 22 May -  12:30 hrs. 




Euler Lecture Hall,  Leonardo Building - terrace level




Vivien LECOMTE  (University of Geneva)




"Large deviations in non-equilibrium 1d systems"



Abstract


Interacting classical particles diffusing in 1d have provided in recent years an interesting playground to study non-equilibrium phenomena.  The dynamics of some of these models is described by an evolution operator,  which can be written as a spin chain Hamiltonian H.  One is interested in the steady state and in the probability that the system presents an atypical current flow.  These are described by large deviation functions (ldf).
Finding the ldf amounts to determining the ground state of H - a task similar to the quantum problems.  I will present different methods (Bethe Ansatz, fluctuating hydrodynamics) used to compute the ldf and to characterize its singularities - which correspond to dynamical phase transitions.  Some class of systems also present an intriguing duality between non-equilibrium and equilibrium, that reveal for instance the origin of long-range correlations induced e.g. by contact with reservoirs of different chemical potential.

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JOINT ICTP/SISSA CONDENSED MATTER SEMINAR



Seminar Room - ICTP Leonardo Building  (first floor)




Wednesday, 27 May -     4:00 p.m.



Uwe BOVENSIEPEN   ( Freie Universität Berlin )



" Femtosecond time-resolved spectroscopy of  the solid state"



Abstract


Solids are characterized by their different degrees of freedom charge, lattice, and spin. Coupling of these degrees of freedom to each other results in fundamental phenomena like superconductivity (electron-phonon coupling) or the Kondo effect (spin-dependent electron scattering). Time-resolved spectroscopy employing femtosecond laser pulses faciliates direct and independent access of these degrees of freedom and occasionally novel insight into coupling mechanisms. In this talk two examples will be presented. (a) Quasi-one dimensional structurs form charge density waves. Using time- and angle-resolved photoelectron spectroscopy we have succeeded to monitor the single and many particle excitations in the charge density wave compound TbTe_3 close to thermodynamic equilibrium. In case of more intense optical excitation non-equilibrium conditions are generated, which finally lead to melting of the charge density wave and facilitate  an identification of the responsible mode. (b) 
Electron injection from a metal substrate into ice layers results in localization and subsequent stabilization of these excess electrons, which occurs by electron-induced rearrangement of water molecules. Due to the permanent electrical dipole moment this process is refered to as electron solvation and we find a pronounced correlation of ice structure and solvation dynamics at such ice-metal interfaces. Electron traps at crystalline ice surfaces, which exhibit extremely long hot electron lifetimes up to minutes, present a model system for specfic reaction sites as demonstrated for electron induced dissociation of Freon adsorbed on ice.
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