Thermalization and photoluminescence dynamics of indirect excitons at low bath temperatures

The thermalization and photoluminescence (PL) dynamics of indirect excitons in GaAs/AlGaAs coupled quantum wells (QWs) at very low bath temperature, T b <1 K, are analysed theoretically and modelled numerically in order to clarify the origin of the recently observed sharp increase of the PL signal (PL-jump) right after a high-intensity excitation pulse. We conclude that the PL-jump effect is mainly due to classical cooling of indirect excitons after the pump pulse, which heats the exciton system. Thus the effect cannot unambiguously be attributed to bosonic stimulation of the scattering processes into the ground-state mode . It is argued that the narrowing effect, i.e. an effective screening of in-plane QW disorder by dipole–dipole interacting indirect excitons, naturally explains the observed strongly nonlinear dependence of the PL rise time on the pump intensity. We also discuss and analyse an evaporative optical heating/cooling effect: the change of the effective temperature T of indirect excitons, due to their resonant optical decay.