The quantum anomalous Hall (QAH) effect is a two-dimensional topological insulating state that has quantized Hall resistance of h/Ce2 and vanishing longitudinal resistance under zero external magnetic field, where C is called Chern number. A QAH system carries spin-polarized dissipation-free chiral edge current. Therefore, the QAH effect may have a considerable impact on future electronic and spintronic device applications for ultralow-power consumption. The QAH effect was first realized in the magnetically doped topological insulator (TI) in 2013[1]. More recently, it was also observed in the intrinsic topological magnet MnBi2Te4 and the moiré materials. In this talk, I will introduce our recent research progress on the QAH effect based on the magnetic topological insulator (TI) multilayers. Through fabricating magnetic TI multilayers, we realized the QAH effect with tunable Chern number up to 5. The Chern number of the QAH multilayers can be tuned by varying either the Cr doping concentration or the thickness of the magnetic TI layer[2]. Utilizing this property, we also studied the Chern number change-induced plateau phase transition between the C = 1 to C = 2 QAH states under zero magnetic field [3]. In the last part of my talk, I will discuss interesting physics and potential applications enabled by the QAH insulators with high tunable Chern numbers[4,5].
[1] C. Z. Chang et al., Science 340, 167 (2013).
[2] Y. F. Zhao et al., Nature 588, 419 (2020).
[3] Y.-F. Zhao, R. Zhang, L.-J. Zhou, R. Mei, Z.-J. Yan, M. H. Chan, C.-X. Liu, and C.-Z. Chang, arXiv preprint arXiv:2109.11382 (2021).
[4] Y. F. Zhao et al., Adv Mater, e2310249 (2023).
[5] Y. F. Zhao, R. Zhang, J. Cai, D. Zhuo, L. J. Zhou, Z. J. Yan, M. H. W. Chan, X. Xu, and C. Z. Chang, Nat Commun 14, 770 (2023).
Bio: Dr. Yi-Fan Zhao is currently a Kavli ENSI postdoctoral research fellow in the Department of Physics at the University of California, Berkeley. He received his Ph.D. in Physics in 2022 from Pennsylvania State University. Dr. Zhao is an expert in the molecular beam epitaxy (MBE) growth and electrical transport measurement of quantum materials, with a particular focus on the QAH insulators. His recent interests have expanded to include electrical transport and scanning probe study of QAH effect in moiré systems.