Abstract:

One of the most important conceptual breakthroughs in modern physics was the discovery of topological phases of quantum matter. An outstanding example is the quantum Hall effect in two-dimensional electron gas subjected to a strong magnetic field, in which the Chern number associated with the discrete Landau level leads to quantized Hall plateaus. More recently, it was discovered that some topological materials exhibit nontrivial band topology even in the absence of magnetic field. In this talk, we will present transport property studies on these novel topological materials. The first topic is about the quantum anomalous Hall effect, which is the quantum Hall effect in zero magnetic field due to spontaneous magnetization. We will show how we fine tune the electronic and magnetic properties of Cr doped (Bi,Se)2Te3 topological insulator thin films grown by molecular beam epitaxy, which eventually led to the observation of quantum anomalous Hall effect. The second topic is about the axion insulator phase, which has zero Chern number but a finite topological Chern-Simons term. Recently, we observed the transport signatures of axion insulator state, namely a large longitudinal resistance and wide zero Hall plateau, in antiferromagnetic topological insulators MnBi2Te4 with an even number of unit cells. These exotic quantum transport phenomena demonstrate the intricate interplay between nontrivial topology and magnetism in topological materials.

王亚愚教授， 1998年本科毕业于中国科技大学物理系，2004年在美国普林斯顿大学物理系获得博士学位，2004年至2007年在美国加州大学伯克利分校物理系担任Miller Research Fellow。2007年12月加入清华大学物理系任教至今。研究领域为凝聚态物理实验，特别是低维强关联电子体系中的新奇物态和微观机理研究，近期的主要研究方向为拓扑量子材料的输运性质和高温超导体的扫描隧道显微学研究。