Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4

by Prof. Yuanbo Zhang (Fundan University)

Wednesday 4 Jun 2025, 10:00 → 11:00 Asia/Shanghai

Tsung-Dao Lee Institute/N4F-N400 - meeting room (Tsung-Dao Lee Institute)

Time: 10:00 June 4 (Wednesday), 2025

Host: Prof. Anyuan Gao

Venue: TDLI Meeting Room N400

Tencent meeting link:  https://meeting.tencent.com/dm/GSxrXWyixW0k Meeting ID:  635649282 , no password

 

Abstract:

In a magnetic topological insulator, the interplay of nontrivial band topology and magnetic order gives rise to intriguing states of matter, most notably exemplified by quantum anomalous Hall (QAH) insulators and axion insulators. These magnetic topological insulators are typically engineered by doping magnetic atoms into topological insulator materials. However, the presence of random magnetic dopants inevitably introduces disorders that impede the thorough exploration of topological quantum effects within the material.

In this context, we focus on MnBi2Te4, a stoichiometric topological insulator that possesses an innate magnetic order. This layered van der Waals crystal is an antiferromagnet in the bulk form, with each layer exhibiting ferromagnetic order (a layer refers to a single structural unit in the out-of-plane direction). Atomically thin MnBi2Te4, however, becomes ferromagnetic when the sample has odd number of layers. We have observed the zero-field QAH effect in specimens composed of five layers. As we further gate the surface states of the QAH insulator under a strong magnetic field, conventional quantum Hall (QH) states emerge. I will discuss the intriguing array of topological states that arise from the intricate interplay between the QAH and QH effects.

 

Biography:

Yuanbo Zhang obtained his Bachelor's degree from Peking University in 2000 and completed his PhD in Physics at Columbia University in 2006. He was as a Miller Research Fellow at the University of California, Berkeley, from September 2006 to June 2009, and later worked as a postdoc research associate at IBM Almaden Research Center from March 2010 to September 2010.

Since 2011, Yuanbo Zhang has been a professor at Fudan University. His research focuses on electronic transport in two-dimensional materials, and he also utilizes a scanning tunneling microscope to probe these materials at the atomic scale.