Polarized interacting exciton gas in quantum wells and bulk semiconductors

TL;DR

This paper presents a mean field theory for calculating exciton binding energies in polarized exciton gases, explaining experimental observations of spin degeneracy breaking and luminescence in GaAs quantum wells.

Contribution

It introduces a novel mean field approach to analyze spin polarization effects on exciton energies and spin relaxation in quantum wells and bulk semiconductors.

Findings

Spin degeneracy breaking at high exciton density explained by inter-excitonic exchange.

Energy level splitting between spin states due to many-body effects.

Spin relaxation time governed by intra-exciton exchange.

Abstract

We develop a theory to calculate exciton binding energies of both two- and three-dimensional spin polarized exciton gases within a mean field approach. Our method allows the analysis of recent experiments showing the importance of the polarization and intensity of the excitation light on the exciton luminescence of GaAs quantum wells. We study the breaking of the spin degeneracy observed at high exciton density $(5 \ \ 10^{10} cm ^2)$. Energy level splitting betwen spin +1 and spin -1 is shown to be due to many-body inter-excitonic exchange while the spin relaxation time is controlled by intra-exciton exchange.