We present a theoretical model that allows us to describe the polariton dynamics in a semiconductor microcavity at large densities, for the case of nonresonant excitation. Exciton-polariton scattering from a thermalized exciton reservoir is identified as the main mechanism for relaxation into the lower polariton states. A maximum in the polariton distribution that shifts towards lower energies with increasing pump power or temperature is shown, in agreement with recent experiments. Above a critical pump power, macroscopic occupancies $(5\mathrm{}\times {10}^4)$ can be achieved in the lowest-energy polariton state. Our model predicts the possibility of Bose-Einstein condensation of polaritons, driven by exciton-polariton interaction, at densities well below the saturation density for CdTe microcavities.

• Received 12 February 2002

DOI:https://doi.org/10.1103/PhysRevB.66.085304