Effect of the external fields in high Chern number quantum anomalous Hall insulators

TL;DR

This paper proposes a method to dynamically tune the Chern number in high Chern number quantum anomalous Hall insulators using an external electric field, enabling control over chiral edge states without altering the structure.

Contribution

It introduces a novel approach to adjust the Chern number via an external electric field, overcoming limitations of previous methods that relied on structural modifications.

Findings

Chern number can be tuned by an external electric field.

Variation in transverse conductance indicates changes in Chern states.

Electric field induces band hybridization, controlling topological properties.

Abstract

A quantum anomalous Hall state with high Chern number has so far been realized in multiplayer structures consisting of alternating magnetic and undoped topological insulator layers. However, in previous proposals, the Chern number can be only tuned by varying the doping concentration or the width of the magnetic topological insulator layers. This drawback largely restrict the applications of dissipationless chiral edge currents in electronics since the number of conducting channels remains fixed. In this work, we propose a way of varying the Chern number at will in these multilayered structures by means of an external electric field applied along the stacking direction. In the presence of an electric field in the stacking direction, the inverted bands of the unbiased structure coalesce and hybridize, generating new inverted bands and collapsing the previously inverted ones. In this way, the number of Chern states can be tuned externally in the sample, without the need of modifying the number and width of the layers or the doping level. We showed that this effect can be uncovered by the variation of the transverse conductance as a function of the electric field at constant injection energy at the Fermi level.