Mesoscopic transport in two-dimensional topological insulators

TL;DR

This paper reviews experimental and theoretical studies on mesoscopic transport in 2D topological insulators, focusing on deviations from quantized conductance due to backscattering and spin-flips in HgTe quantum wells.

Contribution

It provides a comprehensive overview of mechanisms causing conductance deviations in 2D TIs and discusses a model incorporating edge and bulk contributions that aligns with experimental data.

Findings

Quantized conductance is observed in short channels but deviates in longer ones.

Backscattering with spin-flips explains deviations from ideal conductance.

A model including edge and bulk effects reproduces experimental results.

Abstract

Topological states of matter have attracted a lot of attention due to their many intriguing transport properties. In particular, two-dimensional topological insulators (2D TI) possess gapless counter propagating conducting edge channels, with opposite spin, that are topologically protected from backscattering. Two basic features are supposed to confirm the existence of the ballistic edge channels in the submicrometer limit: the 4-terminal conductance is expected to be quantized at the universal value $2e^{2}/h$, and a nonlocal signal should appear due to a net current along the sample edge, carried by the helical states. On the other hand for longer channels the conductance has been found to deviate from the quantized value. This article reviewer the experimental and theoretical work related to the transport in two-dimensional topological insulators (2D-TI), based on HgTe quantum wells in zero magnetic field. We provide an overview of the basic mechanisms predicting a deviation from the quantized transport due to backscattering (accompanied by spin-flips) between the helical channels. We discuss the details of the model, which takes into account the edge and bulk contribution to the total current and reproduces the experimental results.