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
State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, People's Republic of China.
School of Physics, Renmin University of China, Beijing, People's Republic of China.
Nature. 2025 May;641(8061):70-75. doi: 10.1038/s41586-025-08860-z. Epub 2025 Apr 16.
The interplay between nontrivial band topology and layered antiferromagnetism in MnBiTe has opened a new avenue for exploring topological phases of matter. The quantum anomalous Hall effect and axion insulator state have been observed in odd and even number layers of MnBiTe, and the quantum metric nonlinear Hall effect has been shown to exist in this topological antiferromagnet. The rich and complex antiferromagnetic spin dynamics in MnBiTe 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 MnBiTe covered with an AlO 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 MnBiTe paves the way for potential applications in topological antiferromagnetic spintronics.
MnBiTe中不平凡的能带拓扑与层状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MnBiTe的奇数层和偶数层中分别观测到了量子反常霍尔效应和轴子绝缘体态，并且在这种拓扑反铁磁体中已证明存在量子度量非线性霍尔效应。MnBiTe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量子反常霍尔现象，但目前尚无实验观测结果。在此，我们制备了一种覆盖有AlO覆盖层的7重层MnBiTe器件，这使得我们能够在宽参数空间内研究反铁磁量子反常霍尔效应。通过调节栅极电压和垂直磁场，我们发现了一系列量子相变，这些相变可归因于复杂自旋构型对边缘态输运的影响。此外，我们发现与铁磁量子反常霍尔态相比，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，我们提出这些独特特性源于范德华反铁磁体固有的自旋翻转和自旋摆动跃迁。MnBiTe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。
