Jeudi 5 Octobre 2000
Recently, experiments on simple atomic systems have demonstrated some of the fascinating properties of correlated states, i.e., superposition of states with well defined relative phases. However, it remains a challenge to make similar observations in condensed matter. Spectacular progress has been made in the field of ultrafast nonlinear spectroscopy of solids, and in particular of semiconductors. A wealth of valuable and novel information on Coulomb correlation and electronic dynamics in solids has been obtained in regimes where traditional assumptions fail. It becomes possible to observe deviations from mean-field theory.
Recent comparative experimental and theoretical studies have revealed in semiconductors features related to genuine 4-particle and 6-particle correlations. Time resolved spectroscopy with resolution much shorter thanthe scattering time scales have made observable memory effects in electron-electron interaction and electron-phonon interaction in semiconductors. A wide range of phenomena requiring a Quantum-Kinetic theory beyond the Boltzmann limit have been investigated. I will give a comprehensive and balanced account of both experimental and theoretical advances made over the last decade for understanding correlation, decoherence, dephasing and relaxation in condensed matter.