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The quantum anomalous Hall (QAH) effect in van der Waals antiferromagnet MnBi2Te4 harbors a rich interplay between magnetism and topology, holding a significant promise for low-power devices and topological antiferromagnetic (AFM) spintronics. However, this community faces significant challenges as the zero-field quantization depending critically on fabricating high-quality devices. In this talk, I will introduce a straightforward yet effective method to resolve the detrimental effect of standard fabrication on MnBi2Te4 by depositing an AlOx capping layer on the surface before fabrication. 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 exchange gap of the surface state, in stark contrast to that in ferromagnetic (FM) QAH state. In the last part of my talk, I will compare the QAH effect in AFM MnBi2Te4 and FM Cr-doped (Bi,Sb)2Te3 systems, and demonstrate their distinct fate of the QAH phase under a pulsed magnetic field up to 60 T. Through scaling analysis, we find that the QAH effect may exhibit quantum critical behaviors distinct from the conventional quantum Hall phase transition due to the influence of spin fluctuations.
Reference:
[1] Chang Liu et al., Nature Materials, 19, 522 (2020)
[2] Chang Liu et al., PRX 10,041063(2020)
[3] Chang Liu et al., Nature Communications, 12, 4647 (2021)
[4] Yaoxin Li ... Chang Liu#, Nature Communications 15, 3399 (2024)
[5] Yongqian Wang … Chang Liu#, arXiv: 2405.08677
[6] Zichen Lian … Chang Liu#, Jinsong Zhang#, Yayu Wang#, arXiv: 2405.08686
Chang Liu is an associate professor in the Department of Physics at Renmin University of China. He received his bachelor's degree from the School of Physics at Nanjing University in 2013, and completed his doctoral studies at the Department of Physics at Tsinghua University in 2019. From 2016 to 2017, he was a visiting scholar in the Department of Physics at the Massachusetts Institute of Technology. From 2019 to 2022, he served as an assistant researcher in the Department of Quantum State of Matter Beijing Academy of Quantum Information Sciences. In 2022, he joined the Department of Physics at Renmin University of China as an independent principal investigator (PI). Chang's research interests primarily focus on employing quantum transport methods to study novel quantum effects in various two-dimensional materials, magnetic materials, and topological materials. These include the quantum anomalous Hall effect, topological quantum phase transitions, and emergent phenomena under extreme conditions. Currently, he has published 25 articles in journals such as Nature Materials, Nature Physics, Nature Communications, PRL, and PRX.
Tencent meeting link: https://meeting.tencent.com/dm/YSoqirPBvC7E Meeting ID: 445 416 057, no password