Polariton dynamics and Bose-Einstein condensation in semiconductor microcavities

TLDR

The study presents a theoretical model to describe polariton dynamics in semiconductor microcavities under nonresonant excitation at high densities. The model attributes relaxation into lower polariton states primarily to exciton‑polariton scattering from a thermalized exciton reservoir. The model predicts that increasing pump power or temperature shifts the polariton distribution to lower energies, and above a critical pump power yields macroscopic occupancies (~5×10⁴) in the lowest‑energy state, indicating Bose‑Einstein condensation of polaritons at densities below the CdTe microcavity saturation density.

Abstract

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 $(5\ifmmode\times\else\texttimes\fi{}{10}^{4})$ 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.