Renmin University of China

Abstract

The quantum anomalous Hall (QAH) effect in van der Waals topological antiferromagnet MnBi2Te4 harbors a rich interplay between magnetism and topology, holding a significant promise for low-power devices and topological antiferromagnetic (AFM) spintronics. The rich and complex spin dynamics is expected to generate novel AFM QAH phenomena that are absent in ferromagnetic (FM) topological insulators. However, in the past 5 years, the experimental community faces a significant challenge that realizing zero-field quantization depends critically on fabricating high-quality devices. In this talk, I will first introduce how we identify the most critical factor affecting quantization by tracking the anomalous even-odd-layer dependent transport behaviors [1]. Then, I will introduce a straightforward yet effective method to resolve this detrimental influence of standard fabrication on device quality by depositing an AlOx capping layer on MnBi2Te4 surface [2]. By applying the gate voltage and perpendicular magnetic field in a 7-septuple-layer device, we uncover a cascade of quantum phase transitions that can be attributed to the influence of complex AFM spin configurations on edge state transport [3]. Furthermore, we find that an in-plane magnetic field enhances both the coercive field and exchange gap of the surface state, in contrast to that in ferromagnetic QAH state [3]. Our experiments not only pave the way for fabricating high-quality dissipationless device, but also advance the investigation of exotic topological quantum phenomena in 2D materials.

References:

[1] Y. Li et al, Nat. Commun. 15, 3399 (2024).

[2] Y. Wang et al, Nat. Commun. 16, 1727 (2025).

[3] Z. Lian et al, Nature (2025), https://doi.org/10.1038/s41586-025-08860-z

刘畅，中国人民大学物理学院副教授。2013年南京大学物理学院获得学士学位，2019年在清华大学物理系获得博士学位。2016年至2017年，麻省理工学院物理系国家公派博士联合培养。2019年博士毕业后加入北京量子信息科学研究院任助理研究员。2022年，作为独立PI加入中国人民大学物理学院。刘畅的研究兴趣集中在利用输运的实验手段研究低维拓扑材料中的新奇量子效应，近年来通过发展新型的器件制备方法和极端条件测量手段，在量子反常霍尔效应相关的物态构筑和物性调控方向取得一系列创新性成果。目前已发表学术论文28篇，包括以第一和通讯作者身份在Nature, Nature Materials, Nature Communications, PRL, PRX和Adv. Mater.等期刊发表论文14篇，近五年内代表作单篇最高引用840次。