近日，清华大学王亚愚团队研究了自旋翻转和翻转下的反铁磁量子反常霍尔效应。这一研究成果发表在2025年4月16日出版的《自然》杂志上。

MnBi₂Te₄中非平凡能带拓扑和分层反铁磁性之间的相互作用为探索物质的拓扑相开辟了一条新途径。在MnBi₂Te₄的奇数层和偶数层中观察到了量子反常霍尔效应和轴子绝缘体态，并且证明了这种拓扑反铁磁体中存在量子度量非线性霍尔效应。MnBi₂Te₄中丰富而复杂的反铁磁自旋动力学有望产生传统铁磁拓扑绝缘体中不存在的新的量子反常霍尔现象，但实验观察结果仍然未知。

研究组制造了一个覆盖有AlO_x覆盖层的7层MnBi₂Te₄器件，这使其能够在宽参数空间内研究反铁磁量子反常霍尔效应。通过调整栅极电压和垂直磁场，发现了一系列量子相变，这可以归因于复杂自旋配置对边缘态输运的影响。此外，研究组发现，与铁磁量子反常霍尔态相比，平面内磁场增强了表面态的矫顽场和交换能隙。结合数值模拟，他们提出这些特殊特征来自范德华反铁磁体固有的自旋翻转和翻转跃迁。MnBi₂Te₄中量子反常霍尔效应的多功能可调性为拓扑反铁磁自旋电子学的潜在应用铺平了道路。

附：英文原文

Title: Antiferromagnetic quantum anomalous Hall effect under spin flips and flops

Author: Lian, Zichen, Wang, Yongchao, Wang, Yongqian, Dong, Wen-Han, Feng, Yang, Dong, Zehao, Ma, Mangyuan, Yang, Shuai, Xu, Liangcai, Li, Yaoxin, Fu, Bohan, Li, Yuetan, Jiang, Wanjun, Xu, Yong, Liu, Chang, Zhang, Jinsong, Wang, Yayu

Issue&Volume: 2025-04-16

Abstract: The interplay between nontrivial band topology and layered antiferromagnetism in MnBi2Te4 has opened a new avenue for exploring topological phases of matter1,2,3,4. The quantum anomalous Hall effect5 and axion insulator state6 have been observed in odd and even number layers of MnBi2Te4, and the quantum metric nonlinear Hall effect7,8 has been shown to exist in this topological antiferromagnet. The rich and complex antiferromagnetic spin dynamics in MnBi2Te4 is expected to generate new quantum anomalous Hall phenomena that are absent in conventional ferromagnetic topological insulators, but experimental observations are still unknown. Here we fabricate a device of 7-septuple-layer MnBi2Te4 covered with an AlOx capping layer, which enables the investigation of antiferromagnetic quantum anomalous Hall effect over wide parameter spaces. By tuning the gate voltage and perpendicular magnetic field, we uncover a cascade of quantum phase transitions that can be attributed to the influence of complex spin configurations on edge state transport. Furthermore, we find that an in-plane magnetic field enhances both the coercive field and the exchange gap of the surface state, in contrast to that in the ferromagnetic quantum anomalous Hall state. Combined with numerical simulations, we propose that these peculiar features arise from the spin flip and flop transitions that are inherent to a van der Waals antiferromagnet. The versatile tunability of the quantum anomalous Hall effect in MnBi2Te4 paves the way for potential applications in topological antiferromagnetic spintronics9,10.

DOI: 10.1038/s41586-025-08860-z

Source: https://www.nature.com/articles/s41586-025-08860-z