Charge and spin transport in edge channels of a $\nu=0$ quantum Hall system on the surface of topological insulators

TL;DR

This paper investigates charge and spin transport in edge channels of a $ u=0$ quantum Hall system on topological insulator surfaces, revealing helical edge states and proposing experiments for spintronics applications.

Contribution

It provides a theoretical analysis of edge states in $ u=0$ quantum Hall topological insulators and links them to observed nonlocal charge transport and potential spintronics functionalities.

Findings

Gapped helical edge states form on side surfaces under certain conditions.

Edge channels explain nonlocal charge transport observed experimentally.

Spin transport is supported by spin-momentum locking in edge states.

Abstract

Three-dimensional topological insulators of finite thickness can show the quantum Hall effect (QHE) at the filling factor $\nu=0$ under an external magnetic field if there is a finite potential difference between the top and bottom surfaces. We calculate energy spectra of surface Weyl fermions in the $\nu=0$ QHE and find that gapped edge states with helical spin structure are formed from Weyl fermions on the side surfaces under certain conditions. These edge channels account for the nonlocal charge transport in the $\nu=0$ QHE which is observed in a recent experiment on (Bi$_{1-x}$Sb$_x$)$_2$Te$_3$ films. The edge channels also support spin transport due to the spin-momentum locking. We propose an experimental setup to observe various spintronics functions such as spin transport and spin conversion.