Two-dimensional topological insulators in quantizing magnetic fields

TL;DR

This paper investigates how strong magnetic fields affect the edge states and conductance in two-dimensional topological insulators, revealing that helical edge states persist but with altered velocities and reduced conductance due to backscattering.

Contribution

It demonstrates that helical edge states survive under quantizing magnetic fields but exhibit different velocities and suppressed conductance, extending understanding of topological insulators in magnetic environments.

Findings

Helical edge states persist under strong magnetic fields.

Magnetic fields alter the velocities of counter-propagating edge channels.

Backscattering leads to reduced longitudinal conductance.

Abstract

Two-dimensional topological insulators are characterized by gapped bulk states and gapless helical edge states, i.e. time-reversal symmetric edge states accommodating a pair of counter-propagating electrons. An external magnetic field breaks the time-reversal symmetry. What happens to the edge states in this case? In this paper we analyze the edge-state spectrum and longitudinal conductance in a two-dimensional topological insulator subject to a quantizing magnetic field. We show that the helical edge states exist also in this case. The strong magnetic field modifies the group velocities of the counter-propagating channels which are no longer identical. The helical edge states with different group velocities are particularly prone to get coupled via backscattering, which leads to the suppression of the longitudinal edge magnetoconductance.