Attractive and repulsive dipolar interaction in bilayers of indirect excitons

TL;DR

This paper investigates the attractive and repulsive dipolar interactions in bilayers of indirect excitons, revealing conditions under which attraction occurs and demonstrating effects like energy reduction and cloud shift through experiments and simulations.

Contribution

It demonstrates the realization of attractive dipolar interactions in a 2-CQW heterostructure, supported by experimental and theoretical evidence, advancing understanding of exciton interactions.

Findings

Increasing IX density causes energy reduction in the other layer.

IX clouds shift towards each other indicating attraction.

Measured effects exceed predictions of correlated liquid theory.

Abstract

We explore attractive dipolar interaction in indirect excitons (IXs). For one layer of IXs in a single pair of coupled quantum wells (CQW), the out-of-plane IX electric dipoles lead to repulsive dipolar interaction between IXs. The attractive dipolar interaction between IXs is realized in a 2-CQW heterostructure with two IX layers in two separated CQW pairs. We found both in experimental measurements and theoretical simulations that increasing density of IXs in one layer causes a monotonic energy reduction for IXs in the other layer. We also found an in-plane shift of a cloud of IXs in one layer towards a cloud of IXs in the other layer. This behaviour is qualitatively consistent with attractive dipolar interaction. The measured IX energy reduction and IX cloud shift are higher than the values given by the correlated liquid theory.