Towards the Quantized Anomalous Hall effect in AlO$_x$-capped MnBi$_2$Te$_4$

TL;DR

This study demonstrates that depositing an AlO$_x$ layer on MnBi$_2$Te$_4$ enhances the anomalous Hall effect and preserves sample quality, advancing the development of quantum anomalous Hall devices in 2D materials.

Contribution

Introducing a simple AlO$_x$ capping method to improve sample quality and achieve better quantization of the anomalous Hall effect in MnBi$_2$Te$_4$.

Findings

AlO$_x$ capping preserves sample integrity.

Enhanced anomalous Hall effect towards quantization.

Gate-independent antiferromagnetism observed.

Abstract

The quantum anomalous Hall effect in layered antiferromagnet MnBi$_2$Te$_4$ harbors a rich interplay between magnetism and topology, holding a significant promise for low-power electronic devices and topological antiferromagnetic spintronics. In recent years, MnBi$_2$Te$_4$ has garnered considerable attention as the only known material to exhibit the antiferromagnetic quantum anomalous Hall effect. However, this field faces significant challenges as realizing quantized transport at zero magnetic fields depends critically on fabricating high-quality device. In this article, we address the detrimental influences of fabrication on MnBi$_2$Te$_4$ by simply depositing an AlO$_x$ thin layer on the surface prior to fabrications. Optical contrast and magnetotransport measurements on over 50 samples demonstrate that AlO$_x$ can effectively preserve the pristine state of the samples and significantly enhance the anomalous Hall effect towards quantization. Scaling analysis reveals the Berry curvature dominated mechanism of the anomalous Hall effect at various magnetic configurations. By adjusting the gate voltage, we uncover a gate independent antiferromagnetism in MnBi$_2$Te$_4$. Our experiment not only pave the way for fabricating high-quality transport devices but also advance the exploration of exotic quantum physics in 2D materials.