Many-body correlations of electrostatically trapped dipolar excitons

TL;DR

This study investigates the many-body correlations in a cold, two-dimensional liquid of dipolar excitons confined in quantum wells, revealing interaction-driven spectral asymmetries and power-law behaviors in photoluminescence.

Contribution

It provides experimental evidence of correlated dipolar exciton behavior at ultra-low temperatures and densities, highlighting many-body effects in a quasi-equilibrium bosonic system.

Findings

Asymmetric PL lineshape develops with decreasing temperature and increasing density.

PL intensity follows a power law I(E) ∼ (E₀−E)^−|α| with |α| ≈ 0.8 below 5 K.

Spectral features reflect dipolar interaction energies and many-body correlations.

Abstract

We study the photoluminescence (PL) of a two-dimensional liquid of oriented dipolar excitons in In_{x}Ga_{1-x}As coupled double quantum wells confined to a microtrap. Generating excitons outside the trap and transferring them at lattice temperatures down to T = 240 mK into the trap we create cold quasi-equilibrium bosonic ensembles of some 1000 excitons with thermal de Broglie wavelengths exceeding the excitonic separation. With decreasing temperature and increasing density n <= 5*10^10 cm^{-2} we find an increasingly asymmetric PL lineshape with a sharpening blue edge and a broad red tail which we interpret to reflect correlated behavior mediated by dipolar interactions. From the PL intensity I(E) below the PL maximum at E_{0} we extract at T < 5 K a distinct power law I(E) \sim (E_{0}-E)^-|\alpha| with -|\alpha|\sim -0.8 in the range E_{0}-E of 1.5-4 meV, comparable to the dipolar interaction energy.