Dynamical exciton condensates in biased electron-hole bilayers

TL;DR

This paper explores how charge tunneling in biased electron-hole bilayers leads to dynamical exciton condensates exhibiting ac Josephson effects, with implications for tunable light emission and superradiant phases in optical cavities.

Contribution

It introduces the concept of dynamical exciton condensates driven by charge tunneling under bias, connecting exciton physics with Josephson effects and cavity quantum electrodynamics.

Findings

Charge tunneling induces ac Josephson effect in exciton condensates.

Bias control enables switching between bright and dark condensate states.

Coupling to optical cavities leads to superradiant phases depending on bias.

Abstract

Bilayer materials may support interlayer excitons comprised of electrons in one layer and holes in the other. In experiments, a non-zero exciton density is typically sustained by a bias chemical potential, implemented either by optical pumping or by electrical contacts connected to the two layers. We show that if charge can tunnel between the layers, the chemical potential bias means that an exciton condensate is in the dynamical regime of ac Josephson effect. It has physical consequences such as tunneling currents and the ability to tune a condensate from bright (emitting coherent photons) to dark by experimental controlling knobs. If the system is placed in an optical cavity, coupling with cavity photons favors different dynamical states depending on the bias, realizing superradiant phases.