Hidden edge Dirac point and robust quantum edge transport in InAs/GaSb quantum wells

TL;DR

This paper investigates the unique band structure and robustness of quantum edge transport in InAs/GaSb quantum wells, revealing a hidden Dirac point and explaining resilience under magnetic fields.

Contribution

It uncovers the peculiar band evolution and the hidden Dirac point in InAs/GaSb quantum wells, explaining the robustness of edge transport despite magnetic field effects.

Findings

The Dirac point can be buried in the bulk valence bands in deeply inverted regimes.

Zeeman energy gaps open at the Dirac point under magnetic fields.

Quantum edge transport remains robust even with strong magnetic fields.

Abstract

The robustness of quantum edge transport in InAs/GaSb quantum wells in the presence of magnetic fields raises an issue on the fate of topological phases of matter under time-reversal symmetry breaking. A peculiar band structure evolution in InAs/GaSb quantum wells is revealed: the electron subbands cross the heavy hole subbands but anticross the light hole subbands. The topologically protected band crossing point (Dirac point) of the helical edge states is pulled to be close to and even buried in the bulk valence bands when the system is in a deeply inverted regime, which is attributed to the existence of the light hole subbands. A sizable Zeeman energy gap verified by the effective g-factors of edge states opens at the Dirac point by an in-plane or perpendicular magnetic field, however it can also be hidden in the bulk valance bands. This provides a plausible explanation for the recent observation on the robustness of quantum edge transport in InAs/GaSb quantum wells subjected to strong magnetic fields.