Prediction of superconductivity in mass-asymmetric electron-hole bilayers

TL;DR

This paper explores the phase diagram of mass-asymmetric electron-hole bilayers, revealing various correlated phases including exciton condensates, Wigner crystals, and a novel electron-liquid hole-crystal phase, with potential for superconductivity mediated by acoustic plasmons.

Contribution

It introduces the concept of a mixed phase analogous to two-dimensional metallic hydrogen and demonstrates BCS-type superconductivity mediated by acoustic plasmons in these systems.

Findings

Identification of a rich phase diagram including exciton condensates and Wigner crystals.

Prediction of a superconducting phase mediated by acoustic plasmons.

Proposal for experimental realization in van der Waals heterostructures.

Abstract

We study density-balanced, mass-asymmetric electron-hole bilayers as a tunable platform for correlated quantum phases. With independent control of carrier density and interlayer separation, the system exhibits a rich phase diagram, including exciton condensates, Wigner crystals, and for large hole-to-electron mass ratios, an electron-liquid hole-crystal phase. This mixed phase is an analog of two-dimensional metallic hydrogen, featuring an electron liquid immersed in and coupled to a lattice of heavy holes. We show that acoustic plasmons mediate an attractive interaction between electrons, leading to BCS-type superconductivity at experimentally accessible parameters. The superconducting transition temperature is calculated from first principles, and experimental realization in van der Waals heterostructures is discussed.