Dephasing kinetics of a coherent exciton polarization by exciton–exciton scattering
ABSTRACT A system of excitons interacting via a two-particle interaction and with an external light field is treated within a boson approximation. Equations are derived and solved numerically including both the coherent interaction of the excitons and the incoherent x–x scattering on a microscopic level. Anomalous propagators, consisting of two exciton annihilation operators, have been also included. These are found to be necessary for the generation of incoherent excitons after coherent resonant excitation. The complete excitation, thermalization and dephasing kinetics can be studied within our model. A considerable slowing down of the dephasing is found for exciton densities approaching the critical conditions for a Bose–Einstein condensation showing strong deviations from a simple linear excitation-induced dephasing. This can be interpreted as a first sign of the onset of this phase transition.