Seminarium Fizyki Materii Skondensowanej

How is a new stationary state reached in an isolated quantum-mechanical many-body system after it has been forced out of equilibrium? What are the properties of this new state, in particular, is it the thermal state expected from statistical mechanics? For correlated electrons in condensed matter, which are not independent of each other because of the Coulomb interaction, such questions can be investigated with time-resolved femtosecond spectroscopy, where shortly after a first laser pulse the response to a second pulse is measured. In the talk theoretical approaches that describe the real-time dynamics of correlated systems are discussed, with an emphasis on nonequilibrium dynamical mean-field theory for Hubbard-type models. We show how time-resolved spectroscopic data is related to the time-dependent electronic quantum state. We discuss the formation of new stationary states, which is also of interest in view of experiments with cold atomic gases in optical traps. [1] M. Eckstein and M. Kollar, Phys. Rev. Lett. 100, 120404 (2008); [2] M. Kollar and M. Eckstein, Phys. Rev. A 78, 013626 (2008); [3] M. Eckstein and M. Kollar, Phys. Rev. B 78, 205119 (2008); [4] M. Eckstein and M. Kollar, Phys. Rev. B 78, 245113 (2008); [5] M. Eckstein, M. Kollar, and P. Werner, arXiv:0904.0976.