Particle correlations and evidence for dark state condensation in a cold dipolar exciton fluid

TL;DR

This study provides experimental evidence of correlation regimes and a phase transition to a dark state in a cold dipolar exciton fluid within a semiconductor bilayer, revealing complex many-body interactions.

Contribution

It presents the first experimental observation of a transition to a dark exciton state and correlation regimes beyond mean field in a cold dipolar exciton fluid.

Findings

Correlation regimes beyond mean field at higher temperatures

Sharp increase in interaction energy at lower temperatures

Evidence of a macroscopic transition to a dark state

Abstract

In this paper we show experimental evidence of a few correlation regimes of a cold dipolar exciton fluid, created optically in a semiconductor bilayer heterostructure. In the higher temperature regime, the average interaction energy between the particles shows a surprising temperature dependence which is an evidence for correlations beyond the mean field model. At a lower temperature, there is a sharp increase in the interaction energy of optically active excitons, accompanied by a strong reduction in their apparent population. This is an evidence for a sharp macroscopic transition to a dark state as was suggested theoretically.