Quantum Transport Phenomena in Magnetic Topological Insulators
A remarkable breakthrough in the field of topological quantum matter is the discovery of topological insulator (TI) with nontrivial bulk band topology and metallic boundary states. The TIs are expected to host a rich variety of novel quantum transport phenomena, especially when the time reversal symmetry is broken. In particular, the quantum anomalous Hall effect (QAHE), namely the quantum Hall effect in zero magnetic field, may occur in two-dimensional ferromagnetic TIs without Landau levels. In order to realize this effect, the system must fulfill the stringent requirements of being topological, ferromagnetic, and insulating simultaneously. In this talk, we will first give a brief introduction about TI and the QAHE. Then we will show how to fine tune the electronic and magnetic properties in Cr doped (Bi,Se)2Te3 topological insulator thin films grown by molecular beam epitaxy, which eventually led to the observation of QAHE. In the end, we will present more recent developments in this field, including the axion insulator phase and helical Chern insulator phase in the newly discovered MnBi2Te4 antiferromagnetic TI.
Yayu Wang received his B.S. degree in physics from the University of Science and Technology of China in 1998 and his Ph.D. from Princeton University in 2004. From 2004 and 2007 he was a Miller research fellow at UC Berkeley. After a brief visit to MIT, he joined the physics department of Tsinghua University in December 2007. His recent research interests include transport studies of topological insulators and STM studies of high temperature superconductors.
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