Evidence for Helical Edge Modes in Inverted InAs/GaSb Quantum Wells

TL;DR

This study provides experimental evidence for helical edge modes in inverted InAs/GaSb quantum wells, demonstrating their robustness despite bulk conduction and weak magnetic field dependence, supporting their topological insulator nature.

Contribution

First experimental confirmation of helical edge modes in InAs/GaSb quantum wells under realistic conditions.

Findings

Edge modes persist despite sizable bulk conduction.

Weak magnetic field dependence of edge conductance.

Supports the topological insulator behavior of InAs/GaSb quantum wells.

Abstract

We present an experimental study of low temperature electronic transport in the hybridization gap of inverted InAs/GaSb composite quantum wells. Electrostatic gate is used to push the Fermi level into the gap regime, where the conductance as a function of sample length and width is measured. Our analysis shows strong evidence for the existence of helical edge modes proposed by Liu et al [Phys. Rev. Lett., 100, 236601 (2008)]. Edge modes persist inspite of sizable bulk conduction and show only a weak magnetic field dependence - a direct consequence of gap opening away from zone center.