Exciton Liquid in Coupled Quantum Wells

TL;DR

This paper reports the experimental observation of an exciton liquid phase in GaAs/AlGaAs coupled quantum wells, characterized by distinct optical and electrical properties, and formed due to dipolar exciton interactions at low temperature and high density.

Contribution

First experimental evidence of an exciton liquid phase in coupled quantum wells, revealing phase separation and unique optical signatures.

Findings

Identification of a sharp phase boundary between exciton liquid and electron-hole plasma

Distinct photoluminescence spectra for the two phases

Exciton liquid exhibits short-range order due to dipolar interactions

Abstract

Excitons in semiconductors may form correlated phases at low temperatures. We report the observation of an exciton liquid in GaAs/AlGaAs coupled quantum wells. Above a critical density and below a critical temperature the photogenerated electrons and holes separate into two phases, an electron-hole plasma and an exciton liquid, with a clear sharp boundary between them. The two phases are characterized by distinct photoluminescence spectra and by different electrical conductance. The liquid phase is formed by the repulsive interaction between the dipolar excitons, and exhibits a short range order, which is manifested in the photoluminescence lineshape.