Optical conductivity in strongly correlated electron materials

Ultrafast optical phenomena are of fundamental importance in the investigation of electronic structures of strongly correlated electron materials [1]. Starting from the Hamiltonian of a correlated electron material exposed to a time-dependent laser field, we formulate the particle current density. Within a mean-field approximation, we express the current density in terms of the expectation values of quasiparticle density operators by performing the canonical transformation. Within the Heisenberg picture, we solve a set of equations of motion for these quasiparticle densities. Finally we calculate the optical conductivity in several typical systems. [1] R. D. Averitt and A. J. Taylor, J. Phys: Condensed Matter 14, R1357 (2002).