Dynamics of microcavity polaritons in the presence of an electron gas

The dynamics of microcavity polaritons in the presence of an electron gas is experimentally studied through time-resolved photoluminescence under nonresonant excitation. Electrons are shown to accelerate the emission dynamics of the whole system, both in the polariton trap close to the center of the Brillouin zone (k=0) and in the reservoir of large in-plane wave-vector excitonic states. By studying both the bare quantum well and the microcavity sample, the observed features are explained by the interplay between the physics of excitons and that of polariton relaxation.