Exciton correlations in coupled quantum wells and their luminescence blue shift

TL;DR

This paper investigates how dipole-dipole interactions among excitons in coupled quantum wells influence their correlations and luminescence properties, revealing strong correlations and a significant blue shift in emission spectra.

Contribution

It provides a comprehensive analysis of exciton-exciton correlations across temperature and concentration ranges, highlighting the impact on luminescence blue shift and quantum degeneracy suppression.

Findings

Strong multi-particle correlations at low exciton concentrations.

Suppression of quantum degeneracy at high concentrations due to repulsion.

Calculated blue shift of luminescence line as an indicator of correlations.

Abstract

In this paper we present a study of an exciton system where electrons and holes are confined in double quantum well structures. The dominating interaction between excitons in such systems is a dipole - dipole repulsion. We show that the tail of this interaction leads to a strong correlation between excitons and substantially affects the behavior of the system. Making use of qualitative arguments and estimates we develop a picture of the exciton - exciton correlations in the whole region of temperature and concentration where excitons exist. It appears that at low concentration degeneracy of the excitons is accompanied with strong multi-particle correlation so that the system cannot be considered as a gas. At high concentration the repulsion suppresses the quantum degeneracy down to temperatures that could be much lower than in a Bose gas with contact interaction. We calculate the blue shift of the exciton luminescence line which is a sensitive tool to observe the exciton - exciton correlations.