Keldysh field theory of dynamical exciton condensation transitions in nonequilibrium electron-hole bilayers

TL;DR

This paper develops a nonequilibrium field theory to describe exciton condensation in biased electron-hole bilayers, revealing how tunneling affects the effective band gap and temperature, with implications for various quantum well systems.

Contribution

It introduces a novel nonequilibrium field theory framework for interlayer excitons under bias, highlighting the impact of tunneling on excitonic properties and phase transitions.

Findings

Interlayer tunneling reduces the effective band gap.

Tunneling increases the effective temperature for excitons.

The theory has implications for experimental systems like InAs/GaSb and TMD bilayers.

Abstract

Recent experiments have realized steady-state electrical injection of interlayer excitons in electron-hole bilayers subject to a large bias voltage. In the ideal case in which interlayer tunneling is negligibly weak, the system is in quasi-equilibrium with a reduced effective band gap. Interlayer tunneling introduces a current and drives the system out of equilibrium. In this work we derive a nonequilibrium field theory description of interlayer excitons in biased electron-hole bilayers. In the large bias limit, we find that p-wave interlayer tunneling reduces the effective band gap and increases the effective temperature for intervalley excitons. We discuss possible experimental implications for InAs/GaSb quantum wells and transition metal dichalcogenide bilayers.