Optical Probing Novel 2D Electronic Systems

Prof. Xiaodong Xu
University of Washington

Abstract
Two dimensional (2D) electronic systems serve as a fundamental platform for condensed matter physics. The recent discoveries of new classes of 2D materials, such as graphene, transition metal dichalcogenides, and topological insulators, have provided opportunities to investigate new physics and device applications. In the first part of my talk, I will cover our resent optical investigation of atomically thin transition metal dichalcogenides with electrical control. We show that this mono or bilayer semiconductor not only behave as remarkable excitonic systems in the truly 2D limit, but also provide an ideal system for optical generation and electrical control of valley degrees of freedom, which is a manifestation of control of Berry phase effects in Bloch bands. In the second part of may talk, I will show the experimental demonstration of chiral edge photocurrent in nano beams with strong spin-orbit coupling, which resembles the spin Hall effect in GaAs system. We attribute the observation to the chiral nature of the surface spin states generated by the Rashba spin-orbit coupling effect.

Biography
Xiaodong Xu has been an Assistant Professor in the Department of Physics and the Department of Material Science and Engineering at the University of Washington since Sept. 2010. He received his PhD (Physics, 2008) from the University of Michigan and then performed postdoctoral research (2009-2010) at the Center for Nanoscale Systems at Cornell University. Selected awards include DAPRA YFA, NSF Early Career Award, and DoE Early Career Award.