Quantum Anomalous Hall Effect with Higher Plateaus

TL;DR

This paper develops a general theory for the quantum anomalous Hall effect with higher Chern numbers and identifies a material candidate, showing that increased magnetic moments lead to higher Hall conductance plateaus.

Contribution

It introduces a theoretical framework for higher Chern number QAH effects and predicts a specific magnetic topological insulator as a candidate for C=2 QAH state.

Findings

First-principles calculations identify Cr-doped Bi2(Se,Te)3 as a C=2 QAH insulator.

Higher magnetic moments increase Hall conductance plateaus in QAH, opposite to quantum Hall effect.

The theory explains the realization of higher plateaus in magnetic topological insulators.

Abstract

Quantum anomalous Hall (QAH) effect in magnetic topological insulators is driven by the combination of spontaneous magnetic moments and spin-orbit coupling. Its recent experimental discovery raises the question if higher plateaus can also be realized. Here we present a general theory for QAH effect with higher Chern numbers, and show by first-principles calculations that thin film magnetic topological insulator of Cr-doped Bi$_2$(Se,Te)$_3$ is a candidate for the C=2 QAH insulator. Remarkably, whereas higher magnetic field leads to lower Hall conductance plateaus in the integer quantum Hall effect, higher magnetic moment leads to higher Hall conductance plateaus in the QAH effect.