Title: Spin and valley physics in 2D transition metal dichalcogenides
Speaker: Prof. Wang Yao (Department of Physics at UHK)
Time: July 10, 2015 10:00AM
Venue: Academic Conference Center, IOS, CAS
Abstract: The Bloch bands in many crystals have a degenerate set of energy extrema in momentum space known as valleys. For band-edge carriers, the valley index becomes a discrete degree of freedom in addition to spin. In this talk, I will show that in monolayer transition metal dichalcogenides, the pair of valleys which are time-reversal of each other are distinguishable by their opposite values of magnetic moment, Berry curvature, and circularly-polarized optical transition selection rule. This allows the use of valley pseudospin as information carrier for valley based electronics. I will discuss mechanisms to generate and control the spin and valley pseudospin currents, which are at the heart of spin and valley based electronics. These include the valley and spin Hall effects and the nonlinear valley and spin currents response. I will also discuss the valley physics of novel exciton systems in monolayers and heterobilayers.
Biography: Dr. Yao is an Associate Professor of Department of Physics at The University of Hongkong. He received his Ph.D. in Physics from University of California, San Diego in 2006 and was a Postdoc Fellow in The University of Texas at Austin from 2006 to 2008 before he joined The University of Hongkong in 2008. He is the vice president of the Physical Society of Hongkong. And he is the recipient of OCPA Achievement in Asia Award (Robert T. Poe Prize) in 2014 and the recipient of Croucher Innovation Award in 2013. Dr. Yao leads a theoretical group working in an interdisciplinary field across condensed matter physics, quantum physics, and optical physics. His current research interest is on quantum spintronics, and valley and spin physics in atomically thin 2D materials and their heterostructures. He Published 50+ peer-reviewed papers (14 in Nature and Nature sub-journals, 11 in Physical Review Letters). 9 of the papers are cited >100 times.