Electrical Reservoirs for Bilayer Excitons

TL;DR

This paper proposes a method to create and analyze an exciton reservoir in bilayer 2D electron systems by separate contacts, enabling electrical measurement of exciton fluid properties.

Contribution

It introduces a novel approach to establish and probe exciton reservoirs using electrical contacts and derives relationships between equilibration rates and conductances.

Findings

Electrical contacts can maintain exciton reservoirs in bilayer systems.

Equilibration involves virtual intermediate states with free carriers.

Electrical measurements can reveal thermodynamic properties of the exciton fluid.

Abstract

The ground state of two-dimensional (2D) electron systems with equal low densities of electrons and holes in nearby layers is an exciton fluid. We show that a reservoir for excitons can be established by contacting the two layers separately and maintaining the chemical potential difference at a value less than the spatially indirect band gap. Equilibration between the exciton fluid and the contacts proceeds via a process involving virtual intermediate states in which an unpaired electron or hole occupies a free carrier state in one of the 2D layers. We derive an approximate relationship between the exciton-contact equilibration rate and the electrical conductances between the contacts and individual 2D layers when the contact chemical potentials align with the free-carrier bands, and explain how electrical measurements can be used to measure thermodynamic properties of the exciton fluid.