Switching between attractive and repulsive Coulomb-interaction-mediated drag in an ambipolar GaAs/AlGaAs bilayer device

TL;DR

This study investigates Coulomb drag in an ambipolar GaAs/AlGaAs bilayer device, revealing how attractive and repulsive interactions influence interlayer coupling at low carrier densities.

Contribution

It introduces a novel ambipolar device enabling direct comparison of electron-hole and hole-hole Coulomb interactions within the same structure.

Findings

Coulomb drag resistivity varies with interaction type and carrier density.

Attractive electron-hole interactions show different behavior than repulsive hole-hole interactions.

Device design allows exploration of mass effects on interlayer interactions.

Abstract

We present measurements of Coulomb drag in an ambipolar GaAs/AlGaAs double quantum well structure that can be configured as both an electron-hole bilayer and a hole-hole bilayer, with an insulating barrier of only 10 nm between the two quantum wells. The Coulomb drag resistivity is a direct measure of the strength of the interlayer particle-particle interactions. We explore the strongly interacting regime of low carrier densities (2D interaction parameter $r_s$ up to 14). Our ambipolar device design allows comparison between the effects of the attractive electron-hole and repulsive hole-hole interactions, and also shows the effects of the different effective masses of electrons and holes in GaAs.