How correlated Coulomb quantum kinetics affects the optical phase of four-wave-mixing signals

The optical phase of four-wave-mixing (FWM) signals from a ZnSe single quan tum well is analyzed experimentally and theoretically. The focus is on exci tation conditions where the polarization state of the emitted light is dyna mically changing rather than being fixed by selection rules, a case known t o be sensitive to high-order Coulomb correlations. The phase is measured us ing an iterative procedure taking as input FWM signals with real-time resol ution as well as frequency regime data. The results are compared with a mic roscopical density-matrix description using the dynamics controlled truncat ion (DCT) scheme. Mean-field Coulomb interactions, Pauli blocking and trans itions to biexcitons and the two-pair scattering continuum are accounted fo r. Calculations in the coherent limit are able to reproduce the measured ph ases. The correlated two-pair scattering continuum is shown to have a signi ficant impact on the phase.