Department of Physics
Research, teaching and outreach in Physics at UW–Madison

Events

Events at Physics
<< Summer 2009 Fall 2009 Spring 2010 >>
Subscribe your calendar or receive email announcements of events
R. G. Herb Condensed Matter Seminar
Dephasing and disorder effects in quantum spin Hall effect
Date: Thursday, October 1st
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Xincheng Xie, Oklahoma State University
Abstract: The influence of dephasing on the quantum spin Hall effect (QSHE) 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. Moreover, the longitudinal resistance increases linearly with the sample length but is insensitive to the sample width. These characters are in excellent agreement with the recent experimental results [Science 318, 766 (2007)]. In addition, we define a new spin Hall resistance that also exhibits quantum plateaus. In particular, these plateaus are robust against any type of dephasing and therefore, survive in macroscopic samples and better reflect the topological nature of QSHE.

In addition, 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 supports 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. Base on the above-mentioned picture, the phenomena induced by disorder in the quantum spin Hall region and TAI region are directly explained.
Host: Robert Joynt
Add this event to your calendar