Nonlocal transport in a hybrid two-dimensional topological insulator

TL;DR

This paper investigates nonlocal resistance in a HgTe/CdTe quantum well device, revealing quantized values in the quantum spin Hall regime and its robustness, providing insights into topological edge states and their experimental signatures.

Contribution

It demonstrates quantized nonlocal resistance in a hybrid quantum well device and analyzes its dependence on regimes, disorder, and magnetic field, highlighting the fingerprint of helical edge states.

Findings

Quantized nonlocal resistance at 0.25 h/e^2 in the quantum spin Hall regime.

Nonlocal resistance diminishes with disorder and magnetic field.

Transition from quantum spin Hall to quantum Hall regime suppresses nonlocal signals.

Abstract

We study nonlocal resistance in an H-shaped two-dimensional HgTe/CdTe quantum well consist of injector and detector, both of which can be tuned in the quantum spin Hall or metallic spin Hall regime. Because of strong spin-orbit interaction, there always exist spin Hall effect and the nonlocal resistance in HgTe/CdTe quantum well. We find that when both detector and injector are in the quantum spin Hall regime, the nonlocal resistance is quantized at $0.25\frac{h}{e^2}$, which is robust against weak disorder scattering and small magnetic field. While beyond this regime, the nonlocal resistance decreases rapidly and will be strongly suppressed by disorder and magnetic field. In the presence of strong magnetic field, the quantum spin Hall regime will be switched into the quantum Hall regime and the nonlocal resistance will disappear. The nonlocal signal and its various manifestation in different hybrid regimes originate from the special band structure of HgTe/CdTe quantum well, and can be considered as the fingerprint of the helical quantum spin Hall edge states in two-dimensional topological insulator.