Edge Transport in the Trivial Phase of InAs/GaSb

TL;DR

This study investigates edge transport in InAs/GaSb quantum wells, demonstrating persistent edge conduction in the trivial phase and providing evidence that it is non-topological in origin, contrasting with previous topological insulator expectations.

Contribution

It offers a comprehensive characterization of edge conduction in the trivial regime, challenging the assumption that such conduction indicates topological edge states.

Findings

Edge conduction persists in the trivial regime despite bulk quenching.

Edge conduction characteristics vary with temperature, magnetic field, and geometry.

Evidence suggests the observed edge conduction is non-topological.

Abstract

We present transport and scanning SQUID measurements on InAs/GaSb double quantum wells, a system predicted to be a two-dimensional topological insulator. Top and back gates allow independent control of density and band offset, allowing tuning from the trivial to the topological regime. In the trivial regime, bulk conductivity is quenched but transport persists along the edges, superficially resembling the predicted helical edge-channels in the topological regime. We characterize edge conduction in the trivial regime in a wide variety of sample geometries and measurement configurations, as a function of temperature, magnetic field, and edge length. Despite similarities to studies claiming measurements of helical edge channels, our characterization points to a non-topological origin for these observations.