How Correlated Coulomb Quantum Kinetics Affects the Optical Phase of Four-Wave-Mixing Signals

Abstract

The optical phase of four-wave-mixing (FWM) signals from a ZnSe single quantum well is analyzed experimentally and theoretically. The focus is on excitation conditions where the polarization state of the emitted light is dynamically changing rather than being fixed by selection rules, a case known to be sensitive to high-order Coulomb correlations. The phase is measured using an iterative procedure taking as input FWM signals with real-time resolution as well as frequency regime data. The results are compared with a microscopical density-matrix description using the dynamics controlled truncation (DCT) scheme. Mean-field Coulomb interactions, Pauli blocking and transitions to biexcitons and the two-pair scattering continuum are accounted for. Calculations in the coherent limit are able to reproduce the measured phases. The correlated two-pair scattering continuum is shown to have a significant impact on the phase.