Speaker

张海军

南京大学教授

Date＆Time

2023.07.05（Wed.）AM 9:00

Location

吉林大学中心校区唐敖庆楼B区521报告厅

Reporter

        张海军，南京大学教授，长期从事计算凝聚态物理方面的前沿基础研究，探索和理解凝聚态物理中的各种新奇物性，特别在拓扑量子材料探索和拓扑物性研究方面取得了一些具有国际影响力的原创性研究成果。与合作者，发现了一系列代表性的拓扑量子材料体系（Bi2Se3家族拓扑绝缘体、MnBi2Te4家族本征磁性的轴子绝缘体，2M-WS2二维材料拓扑超导）；原创性提出了基于最局域Wannier函数的拓扑物性数值计算方法等。目前发表SCI学术论文80余篇，论文总引用超过17500次。

Abstract

        The recently discovered MnBi2Te4-family magnetic topological insulators (TIs), have aroused great attention, where the interlayer vdW gap is expected to play a crucial role in topological surface states. Here, we develop a simple Dirac-fermion approach which is valuable to understand and design magnetic topological states in various multilayers of layered magnetic topological insulators. Based on the Dirac-fermion approach, we demonstrate how to understand and tune high Chern numbers in ferromagentic MnBi$_{2}$Te$_{4}$ films through the van der Waals (vdW) gap modulation. We also apply the Dirac-fermion approach to the surface states of vdW antiferromagnetic TIs. Remarkably, unexpected topologically protected gapless Dirac-cone surface states are found to arise under a slight surface vdW gap expansion, if the surface ferromagnetic layer has a zero Chern number, while the surface states remain gapped for all other cases. The unexpected gapless Dirac-cone states are invaluable in solving the puzzle of the observed gapless surface states in MnBi2Te4.