Microwave Photocurrent from the Helical Edge state of InAs/GaInSb Bilayers

TL;DR

This study demonstrates microwave photocurrent as a potential probe for helical edge states in InAs/GaInSb bilayers, revealing edge-specific responses consistent with quantum spin Hall insulator behavior.

Contribution

It introduces microwave photocurrent measurement as a novel method to investigate helical edge states in quantum spin Hall insulators.

Findings

Photocurrent is negligible in Corbino disk bulk samples.

Clear photocurrent signals are observed in Hall bar edge states.

Photocurrent may encode information about edge state properties.

Abstract

We measure microwave photocurrent in devices made from InAs/GaInSb bilayers where both insulating bulk state and conducting edge state were observed in the inverted-band regime, consistent with the theoretical prediction for a quantum spin Hall (QSH) insulator. It has been theoretically proposed that microwave photocurrent could be a unique probe in studying the properties of QSH edge states. To distinguish possible photoresponse between bulk state and helical edge state, we prepare Hall bar and Corbino disk from the same wafer. Results show that the Corbino disk samples have a negligible photocurrent in the bulk gap while clear photocurrent signals from the Hall bar samples are observed. This finding suggests that the photocurrent may carry information concerning the electronic properties of the edge states.