【7月6日】Topological superconductivity and Majorana zero mode

2018-06-21

主讲人:徐刚 教授

地点:理学院454

时间:2018年7月6日下午3:30 

组织单位:理学院计算物理组

报告人简介:

徐刚,男、教授、博导、十三批“青年千人”计划。 2010年于中科院物理所获博士学位,2010-2012于中科院物理所助理研究员,2012-2016于美国斯坦福大学访问学者,2017年至今于华中科技大学国家脉冲强磁场中心工作。主要从事关联电子体系与非常规超导、拓扑物质态、新型二维功能材料的第一性原理计算研究,发表论文36篇,其中PRL八篇,Nat. Nanotech.两篇,Nat. Phys.和 Nat. commun.各一篇,Nano letters 两篇;两篇EPL论文入选“2008年中国百篇最具影响国际学术论文”,总引用4500多次。(1)成功预言了铁基超导母体材料中的条纹状反铁磁基态——铁基超导获得国家自然科学一等奖的代表性工作之一。(2)把凝聚态中电子态按照拓扑分类的概念从绝缘体推广到了半金属,首次提出双外尔半金属的概念,开启了Weyl费米子的研究热潮。

报告摘要:

As one of the simplest systems for realizing Majorana fermions, the topological superconductor (TSC) plays an important role in both condensed matter physics and quantum computations. In this talk, I will introduce some basic concepts and experimental scheme of TSC. Then two specific proposals will be expatiated. (1) In half metal (with compatible SOC)/s-wave superconductor heterostructures, our calculations show that a zigzag edge of the monolayer MX2 terminated by metal atom M has edge states with strong spin-orbit coupling and spontaneous magnetization. By proximity coupling with a superconducting substrate, TSC can be induced at such edge. We propose NbS2 as a natural choice of substrate, and predict that Majorana zero modes (MZMs) can be detected at the 120 degree corner. (2) In the ‘superconducting topological metals’, we show that the three-dimensional extended s-wave Fe-based superconductors such as FeSe0.5Te0.5 have a metallic topologically nontrivial band structure, and exhibit a normal-topological-normal superconductivity phase transition on the (001) surface by tuning the bulk carrier doping level. In the TSC phase, a MZM is trapped at the end of a magnetic vortex line. We further show that the surface TSC phase only exists up to a certain bulk pairing gap. These results pave an effective way to realize the TSC and Majorana fermions in a large class of superconductors.

报告主持:梁拥成

报告语言:中文