Please post and forward to your groups ______________________ CENTER FOR EXCITONICS Optoelectronics of 2D Materials November 25, 2014 at 4:30 PM/ 6-120 Xiaodong Xu University of Washington [xiaodongXu-02] Abstract: Electronic valleys are extrema of Bloch energy bands in momentum space. Having multiple valleys gives the electron states pseudospin degrees of freedom in addition to their real spin. In this talk, I will discuss our experimental progress on the investigation of spins and pseudospins using atomically thin semiconductors, which are either single or bilayer group VI transition metal dichalcogenides [1-3]. These new 2D semiconductors behave as remarkable excitonic systems, providing an exciting laboratory for optical, electrical and magnetic control of the valley degrees of freedom. I will also discuss strong coupling effects between spin, valley, and layer pseudo-spins in bilayers, which lead to spin polarization in electronic bands in the presence of bulk inversion symmetry and allow electrical control of spin states. I will conclude the talk with the discussion of spatially indirect exciton properties in monolayer semiconducting heterostructures [4] and single quantum emitters in monolayers [5]. References [1] Xu et al., Nature Physics 10, 343(2014). [2] Jones et al., Nature Nanotechnology 8, 634-638 (2013). [3] Aivazian et al., http://arxiv.org/abs/1407.2645. [4] Rivera et al., http://arxiv.org/abs/1403.4985; [5] He et al., http://arxiv.org/abs/1411.2449. Bio: Xiaodong Xu has been an Assistant Professor in the Department of Physics and the Department of Materials 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. His nanoscale optoelectronics group at University of Washington focuses on creation, control, and understanding of novel optoelectronic devices based on two-dimensional quantum materials. Selected awards include DAPRA YFA, NSF Early Career Award, DoE Early Career Award, Cottrell Scholar Award, and IUPAP Young Scientist Prize in Semiconductor Physics. Light refreshments will be served