摘要

The influence of dephasing on the quantum spin Hall effect (QSHE) appearing in 2D topological insulator (TI) is studied. In the absence of dephasing, the longitudinal resistance in a QSHE system exhibits the quantum plateaus. We find that these quantum plateaus are robust against the normal dephasing but fragile with the spin dephasing. Thus, these quantum plateaus only survive in mesoscopic samples. In addition, we define a new spin Hall resistance that also exhibits quantum plateaus. In particular, these plateaus are robust against any type of dephasings and therefore, survive in macroscopic samples and better reflect the topological nature of QSHE.

We also study the disorder effect on the transport properties in QSHE. We confirm that at a moderate disorder strength, the initially un-quantized two terminal conductance becomes quantized, and the system makes a transition to the novel topological Anderson insulator (TAI). Conductances calculated for the stripe and cylinder samples reveal the topological feature of TAI and support the idea that the helical edge states may cause the anomalous quantized plateaus. The influence of disorder is studied by calculating the distributions of local currents. Based on the above-mentioned picture, the phenomena induced by disorder in the quantum spin Hall region and TAI region are directly explained.

报告人简介

1982年中国科技大学近代物理系毕业，同年通过Cuspea选拔考试赴美深造。1988年在美国马里兰大学获博士学位。1988年至1991年在美国华盛顿大学、马里兰大学做博士后。1991年至2004年在美国Oklahoma State University任助教授、副教授、教授。2004年任校董事会讲座教授。2000年受聘为中科院国际量子结构中心成员，2005-2006年任中心主任。2001年获得中科院海外知名学者，2002年获得国家杰出青年基金海外类资助，2005年应聘为中科院物理所首席研究员、凝聚态理论与材料计算研究室主任。2010年任北京大学讲席教授、国际量子材料科学中心主任。共发表SCI文章100多篇，包括30余篇PRL文章。现任科技部重大科学研究计划项目（973计划）首席科学家。现主持一项中科院方向性项目，一项基金委重点项目，长期以来得到美国NSF和DOE的连续支持。为美国物理学会(APS) Fellow。主要研究方向为量子霍尔效应、电荷及自旋输运、低维量子体系、关联电子系统。