Multi-probe analysis to separate edge currents from bulk currents in quantum spin Hall insulators and to analyze their temperature dependence

TL;DR

This paper introduces a multi-probe transport analysis method to distinguish between edge and bulk currents in quantum spin Hall insulators, revealing temperature-dependent behaviors and the role of charge impurities.

Contribution

The study develops a novel multi-probe analysis technique to separately evaluate edge and bulk conductivities in large Hall bar devices of InAs/GaInSb quantum wells.

Findings

Dissipative edge currents are present in the topological gap.

Edge conductivity shows weak temperature dependence consistent with helical edge electrons.

Charge impurities linked to Ga-antisite defects influence backscattering.

Abstract

We present a multi-probe transport analysis that effectively separates bulk and edge currents in large Hall bar devices with standard geometries. Applied to transport measurements on all possible four-probe configurations of six-probe Hall bar devices made of inverted three-layer InAs/GaInSb quantum wells (QWs), our analysis not only reveals the presence of dissipative edge currents in the topological gap, but also allows the temperature dependence of bulk and edge conductivity to be evaluated separately. The temperature dependence of the edge conductivity for Hall bar channels from 10 $\mu$m to 70~$\mu$m in the range of 1.5 K to 45 K is consistent with the theoretical expectation of weakly interacting helical edge electrons with backscattering due to localized magnetic moments of charge impurities. We argue that these charge impurities are naturally associated with intrinsic Ga-antisite defects, which act as double acceptors in InAs/Ga(In)Sb-based QWs.