Strong interlayer charge transfer due to exciton condensation in an electrically-isolated GaAs quantum well bilayer

TL;DR

This paper presents a novel GaAs quantum well bilayer system with controllable charge transfer, enabling the study of exciton condensation and interlayer correlations through capacitance and tunneling measurements.

Contribution

It introduces a floating bilayer GaAs quantum well design that allows independent density control and direct measurement of interlayer charge transfer, revealing exciton condensation signatures.

Findings

Enhanced inter-layer tunneling current at total filling factor of 1

Observation of exciton condensation signatures

Full control of individual layer densities

Abstract

We introduce a design of electrically isolated floating bilayer GaAs quantum wells (QW) in which application of a large gating voltage controllably and highly reproducibly induces charges that remain trapped in the bilayer after removal of the gating voltage. At smaller gate voltages, the bilayer is fully electrically isolated from external electrodes by thick insulating barriers. This design permits full control of the total and differential densities of two coupled 2D electron systems. The floating bilayer design provides a unique approach for studying systems inaccessible by simple transport measurements. It also provides the ability to measure the charge transfer between the layers, even when the in-plane resistivities of the 2D systems diverge. We measure the capacitance and inter-layer tunneling spectra of the QW bilayer with independent control of the top and bottom layer electron densities. Our measurements display strongly enhanced inter-layer tunneling current at the total filling factor of 1, a signature of exciton condensation of a strongly interlayer-correlated bilayer system. With fully tunable densities of individual layers, the floating bilayer QW system provides a versatile platform to access previously unavailable information on the quantum phases in electron bilayer systems.