题  目：Disorder-induced topological phase transitions from trivial-to-nontrivial insulators

内容简介：Occurrence of topological Anderson insulator (TAI) in HgTe quantum well suggests that when time-reversal symmetry (TRS) is maintained, the pertinent topological phase transition, marked by re-entrant 2e^2/h quantized conductance contributed by helical edge states, is driven by disorder. In this talk, I will show that when TRS is broken, the physics of TAI becomes even richer. The pattern of longitudinal conductance and nonequilibrium local current distribution displays novel TAI phases characterized by nonzero Chern numbers, indicating the occurrence of multiple chiral edge modes. Unlike topological insulators with time-reversal symmetry that, in the absence of an external magnetic field, support only a single quantized conductance TAI, systems without time-reversal symmetry exhibit novel TAI by tuning either disorder or Fermi energy (in both topologically trivial and nontrivial phases), drives transitions between distinct TAI phases  characterized by jumps of the quantized conductance from 0 to e^2/h and from e^2/h to 2e^2/h. An effective medium theory based on the Born approximation yields an accurate description of different TAI phases in parameter space.

报告人：香港科技大学物理系  王向荣  教授

报告人简介：1984年毕业于武汉大学物理系，同年通过中美联合招收物理研究生选拨考试(CUSPEA) 赴美深造；1990年在美国罗彻斯特大学(University of Rochester)获博士学位；是多所学校和研究机构的客座教授。王教授在凝聚态理论领域具有丰富研究经验，研究领域包括量子霍尔效应，二维电子气量子输运，超晶格以及量子纠缠与量子计算；创造性地提出了超晶格中电流自振荡的极限环理论；从理论上揭示了磁动力学中磁畴壁运动的机理，为完全理解磁畴壁的运动规律提供了理论基础；已在国际权威学术杂志发表论文过百篇。

主持人：陈芝得  教授

时  间：2016年11月21日（周一）下午3：00始

地  点：南海楼338室

热烈欢迎广大师生参加!

信息科学技术学院/网络空间安全学院

2016年11月16日