Energy gap tuning and gate-controlled topological phase transition in InAs/In$_{x}$Ga$_{1-x}$Sb composite quantum wells

TL;DR

This study demonstrates control over the energy gap and topological phase transitions in InAs/InGaSb quantum wells using structural parameters and electric fields, enabling potential electrical switching of edge transport.

Contribution

It introduces a method to tune the energy gap and induce topological phase transitions in composite quantum wells via electric fields and structural design.

Findings

Achieved a 35 meV energy gap in highly strained CQWs.

Demonstrated electric-field-driven topological phase transition.

Observed re-entrant behavior of the energy gap.

Abstract

We report transport measurements of strained InAs/In$_{x}$Ga$_{1-x}$Sb composite quantum wells (CQWs) in the quantum spin Hall phase, focusing on the control of the energy gap through structural parameters and an external electric field. For highly strained CQWs with $x = 0.4$, we obtain a gap of 35 meV, an order of magnitude larger than that reported for binary InAs/GaSb CQWs. Using a dual-gate configuration, we demonstrate an electrical-field-driven topological phase transition, which manifests itself as a re-entrant behavior of the energy gap. The sizeable energy gap and high bulk resistivity obtained in both the topological and normal phases of a single device open the possibility of electrical switching of the edge transport.