Electric field-induced edge state oscillations in GaSb/InAs quantum wells

TL;DR

This paper demonstrates that electric field-induced gap oscillations in GaSb/InAs quantum wells serve as a reliable signature of topologically protected helical edge states, aiding the identification of quantum spin Hall insulator phases.

Contribution

It introduces electric field-induced gap oscillations as a new experimental signature for detecting helical edge states in GaSb/InAs quantum wells.

Findings

Oscillations appear in narrow samples as the system approaches the topological phase.

The study uses a realistic $k \, p$ band theory-based model.

Results guide experimental efforts to identify topological edge states.

Abstract

Inverted-gap GaSb/InAs quantum wells have long been predicted to show quantum spin Hall insulator (QSHI) behavior. The experimental characterization of the QSHI phase in these systems has relied on the presence of quantized edge transport near charge neutrality. However, experimental data showing the presence of edge conductance in the \emph{trivial} regime suggest that additional experimental signatures are needed to characterize the QSHI phase. Here we show that electric field- induced gap oscillations can be used as an indicator of the presence of helical edge states in system. By studying a realistic low-energy model GaSb/InAs quantum wells derived from $k \cdot p$ band theory, we show that such oscillations are bound to appear in narrow samples as the system is driven to the the the topological phase by the electric field. Our results can serve as a guide for the search of additional experimental signatures of the presence of topologically-protected helical edge states in GaSb/InAs systems.