Origin of the inner ring in photoluminescence patterns of quantum well excitons

TL;DR

This paper develops a microscopic model to explain the inner ring pattern in photoluminescence of quantum well excitons, attributing it to exciton cooling during propagation, and provides quantitative estimates of diffusion and disorder.

Contribution

It introduces a coupled nonlinear equations approach to model PL patterns and unambiguously identifies the inner ring origin as exciton cooling.

Findings

Inner ring caused by exciton cooling during propagation

Diffusion coefficient estimated at 10-30 cm^2/s

Disorder potential amplitude about 0.45 meV

Abstract

In order to explain and model the inner ring in photoluminescence (PL) patterns of indirect excitons in GaAs/AlGaAs quantum wells (QWs), we develop a microscopic approach formulated in terms of coupled nonlinear equations for the diffusion, thermalization and optical decay of the particles. The origin of the inner ring is unambiguously identified: it is due to cooling of indirect excitons in their propagation from the excitation spot. We infer that in our high-quality structures the in-plane diffusion coefficient is about 10-30cm^2/s and the amplitude of the disorder potential is about 0.45meV.