REAL-TIME APPROACH TO RELAXATION AND DEPHASING PROCESSES IN SEMICONDUCTORS

Starting from the kinetic equations for the nonequilibrium Green's functions, a practical method is proposed which allows to solve the set of equations for the two-time propatgators numerically. In contrast to the usual semiconductor Bloch equations with phenomenologial damping relaxation and dephasing processes are treated microscopically for the case of coupling to a bath of LO-phonons. Beside a standard approximation for the treatment of LO-phonon scattering, no further approximations are performed. For the low-density limit we compare exact results with approximate treatments, as the Marcovian and non-Marcovian approximations resulting from a density matrix approach. First results concerning nonlinear optical properties are presented.