Electrically Controlled Two-Dimensional Electron-Hole Fluids

TL;DR

This paper investigates the electronic properties of dual-gated electron-hole bilayers with an opaque barrier, explaining how gate voltages control densities and pairing, supported by theoretical analysis and recent experiments.

Contribution

It introduces a combined electrostatic, thermodynamic, and mean-field approach to understand gate-controlled electron-hole densities and pairing in bilayers with tunneling effects.

Findings

Electron and hole densities depend on gate voltages and chemical potential jumps.

A finite gate voltage region exists where electron-hole densities are equal.

The model explains recent experimental results with tunneling and non-equilibrium transport.

Abstract

We study the electronic properties of dual-gated electron-hole bilayers in which the two layers are separated by a perfectly opaque tunnel barrier. Combining an electrostatic and thermodynamic analysis with mean-field theory estimates of interacting system chemical potentials, we explain the dependence of the electron and hole densities on the two gate voltages. Because chemical potential jumps occur for both electrons and holes at neutrality, there is a finite area in gate voltage parameter space over which electron and hole densities are equal. In that regime the electron-hole pair density depends only on the sum of the two gate voltages. We are able to explain a recent experimental study of electrically controlled bilayers by allowing for interlayer tunneling and using a non-equilibrium steady-state transport picture.