Quantum anomalous Hall effect with field-tunable Chern number near Z2 topological critical point

TL;DR

This paper demonstrates that in a specific topological insulator material, the quantum anomalous Hall effect with tunable Chern numbers can be achieved by adjusting exchange fields, sample thickness, and electric fields near a topological critical point.

Contribution

It introduces a practical method to realize and control QAH phases with different Chern numbers in a magnetically doped topologically trivial insulator, reducing the required exchange coupling.

Findings

QAH phases with various Chern numbers can be achieved by tuning exchange field or thickness.

A perpendicular electric field can also tune the Chern number.

The mechanism simplifies realization compared to traditional surface state approaches.

Abstract

We study the practicability of achieving quantum anomalous Hall (QAH) effect with field-tunable Chern number in a magnetically doped, topologically trivial insulating thin film. Specifically in a candidate material, TlBi(S$_{1-\delta}$Se$_{\delta}$)$_2$, we demonstrate that the QAH phases with different Chern numbers can be achieved by means of tuning the exchange field strength or the sample thickness near the Z2 topological critical point. Our physics scenario successfully reduces the necessary exchange coupling strength for a targeted Chern number. This QAH mechanism differs from the traditional QAH picture with a magnetic topological insulating thin film, where the "surface" states must involve and sometimes complicate the realization issue. Furthermore, we find that a given Chern number can also be tuned by a perpendicular electric field, which naturally occurs when a substrate is present.