Analysis of disorder-induced dephasing

A number of experiments yielded a polarization-dependent decay of the time-integrated four-wavemixing (TI-FWM). Often, the TI-FWM decays more rapidly for linear perpendicular than for linear parallel polarized incident pulses. It was suspected that this difference in the decay times is related to the inhomogeneous linewidth of the exciton, i.e. to disorder [1], On the other hand, it was demonstrated in a large number of recent publications, that the understanding of polarization-dependent FWM and pump-probe experiments following excitonic excitation requires the treatment of Coulomb correlations beyond the Hartree-Fock level. For not too strong disorder, these correlations still remain important and influence the nonlinear optical response [2]. A meaningful analysis of disorder effects thus has to include correlations.