Experimental Study of the Exciton Gas Liquid Transition in Coupled Quantum Wells

TL;DR

This study investigates the phase transition of excitons in coupled quantum wells, revealing a liquid state at low temperatures and high laser power, with evidence suggesting quantum liquid behavior.

Contribution

The paper provides the first detailed phase diagram and experimental evidence of a quantum liquid phase in exciton systems within coupled quantum wells.

Findings

Phase transition occurs below 4.8K at high laser power

Latent heat varies linearly with temperature below 1.1K

Disorder is suppressed and diffusion increases sharply below Tc

Abstract

We study the exciton gas-liquid transition in GaAs/AlGaAs coupled quantum wells. Below a critical temperature, Tc=4.8K, and above a threshold laser power density the system undergoes a phase transition into a liquid state. We determine the density temperature phase diagram over the temperature range 0.1 to 4.8K. We find that the latent heat increases linearly with temperature at T<1.1K, similarly to a Bose Einstein condensate transition, and becomes constant at 1.1<T<4.8K. Resonant Rayleigh scattering measurements reveal that the disorder in the sample is strongly suppressed and the diffusion coefficient sharply increases with decreasing temperature at T<Tc, allowing the liquid to spread over large distances away from the excitation region. We suggest that our findings are manifestations of a quantum liquid behavior.