Dephasing in the quasi-two-dimensional exciton-biexciton system

The polarization decay in the exciton-biexciton system of a homogeneously broadened single quantum well is studied by transient four-wave mixing. All three decay rates in the exciton-biexciton three-level system are deduced. The relation between the rates unravels correlations between scattering processes of excitons and biexcitons. Density and temperature dependences show that the involved processes are mainly radiative decay and phonon scattering. The radiative decay rate of the biexcitons is found to be comparable to the one of the excitons, and the involved spontaneous photon emissions from excitons and biexcitons are mutually uncorrelated. In contrast, the biexciton phonon scattering is twice as fast and correlated to exciton-phonon scattering, indicating the interaction with similar phonon modes.