Strongly enhanced topological quantum phases in dual-surface AlO$_x$-encapsulated MnBi$_2$Te$_4$

TL;DR

This paper introduces a wax-assisted exfoliation and AlO$_x$ encapsulation method that significantly enhances topological quantum phases in MnBi$_2$Te$_4$, enabling robust experimental observation of axion insulator and quantum anomalous Hall states.

Contribution

The study presents a novel fabrication technique that improves the quality and topological properties of MnBi$_2$Te$_4$ heterostructures, facilitating the exploration of quantum phenomena.

Findings

Observation of robust axion insulator state in even-layer devices

Detection of quantum anomalous Hall effect in odd-layer devices

Enhanced topological quantum phases due to improved device fabrication

Abstract

The topological quantum phases in antiferromagnetic topological insulator MnBi$_2$Te$_4$ hold promise for next-generation spintronics, but their experimental realization has been constrained by challenges in preparing high-quality devices. In this work, we report a new wax-assisted exfoliation and transfer method that enables the fabrication of MnBi$_2$Te$_4$ heterostructures with both surfaces encapsulated by AlO$_x$. This strategy strongly enhances the topological quantum phases in MnBi$_2$Te$_4$ flakes. We observe the robust axion insulator state in even-layer device with wide zero Hall plateau and high longitudinal resistivity, and the quantum anomalous Hall effect in odd-layer device with large hysteresis and sharp plateau transition. These results demonstrate that the combination of wax exfoliation and AlO$_x$ encapsulation provides great potentials for exploring novel topological quantum phenomena and potential applications in MnBi$_2$Te$_4$ and other two-dimensional materials.