Large bandgap quantum anomalous hall insulator in a designer ferromagnet-topological insulator-ferromagnet heterostructure

TL;DR

This study demonstrates a heterostructure combining ferromagnetic insulators and topological insulators that exhibits a large, room-temperature quantum anomalous Hall effect with a significant bandgap, advancing potential for lossless electronic devices.

Contribution

The paper reports the successful growth and characterization of a MnBi2Te4/Bi2Te3 heterostructure showing a large bandgap and magnetic properties consistent with quantum anomalous Hall insulators at higher temperatures.

Findings

Observed a 75 meV bandgap in the heterostructure.

Confirmed magnetic origin of the gap via broken time reversal symmetry.

Theoretical calculations agree with experimental results.

Abstract

Combining magnetism and nontrivial band topology gives rise to quantum anomalous Hall (QAH) insulators and exotic quantum phases such as the QAH effect where current flows without dissipation along quantized edge states. Inducing magnetic order in topological insulators via proximity to a magnetic material offers a promising pathway towards achieving QAH effect at high temperature for lossless transport applications. One promising architecture involves a sandwich structure comprising two single layers of MnBi2Te4 (a 2D ferromagnetic insulator) with ultra-thin Bi2Te3 in the middle, and is predicted to yield a robust QAH insulator phase with a bandgap well above thermal energy at room temperature (25 meV). Here we demonstrate the growth of a 1SL MnBi2Te4 / 4QL Bi2Te3 /1SL MnBi2Te4 heterostructure via molecular beam epitaxy, and probe the electronic structure using angle resolved photoelectron spectroscopy. We observe strong hexagonally warped massive Dirac Fermions and a bandgap of 75 meV. The magnetic origin of the gap is confirmed by the observation of broken time reversal symmetry and the exchange-Rashba effect, in excellent agreement with density functional theory calculations. These findings provide insights into magnetic proximity effects in topological insulators, that will move lossless transport in topological insulators towards higher temperature.