Université Toulouse III - Paul Sabatier - Bat. 3R4 - 118 route de Narbonne - 31062 Toulouse Cedex 09 - France

Accueil > Événements > Séminaires 2014

Direct visualization of electronic states in photoexcited crystals

Luca PERFETTI, Laboratoire des Solides Irradiés UMR Ecole Polytechnique-CNRS

The recent developments of femtosecond photon sources in the ultraviolet spectral range have largely enriched the techniques to probe condensed matter on ultrafast timescales. Among the possible approaches, time resolved photoemission spectroscopy displays an increasing popularity because of the unique capability to visualize the temporal evolution of electronic states. I will review the basic principles of this experimental method and discuss the most relevant results that have been published in the recent years. The seminar will introduce in a pedagogical form the dynamics of coherent phonon generation and of the electronic thermalization. I will emphasize the additional information that can be obtained by time resolved photoemission with respect to all-optical experiments. Then, I will introduce the physics of systems where many-body interactions are strong enough to induce a phase transition towards an order state. The brief overview of Mott insulators, charge density waves and superconductors will elucidate the mechanism leading to the broken symmetry in each case. Despite the complexity of these problems, I will show that the evolution of the electronic states can provide new insights to discriminate the interplay among many-body interactions. Finally, some perspectives on next generation sources and proposed experiments will offer a general view on the future directions in this research field.