Spin-valleytronics in the moiré pattern of van der Waals heterostructures
Speaker: Wang YAO (Department of Physics, University of Hong Kong)
Time: June 08, 2017 16:00
In monolayer transition metal dichalcogenides (TMDs), a newly emerged class of 2D semiconductors, the low energy carriers are described by massive Dirac cones located at K and -K corners (valleys) of the Hexagonal Brillouin zone. These massive Dirac Fermions have interesting phenomena associated with their valley index, including the valley optical transition selection rules and valley Hall effects, which enable the use of both valley and spin (via spin-valley coupling) as information carriers in future electronics. Van der Waals stacking of 2D semiconductors into heterostructures further provides a powerful approach towards designer quantum materials that extend the exotic properties of the building blocks. As a generic aspect of these vdW heterostructures, the inevitable lattice mismatch always leads to the formation of moiré pattern (i.e. periodic variation of local atomic registries). I will show that the vdW moiré can endow heterostructures unprecedented properties, including electrically switchable lateral superstructures of topological Insulators, nano-patterned spin optics, and spin-orbit coupled excitonic superlattices.
Bio: Dr. Yao received his BSc from Peking University in 2001, and PhD in Physics from the University of California, San Diego in 2006. After two years undertaking postdoctoral work at University of Texas at Austin, he joined the University of Hong Kong as Assistant Professor in 2008, and was promoted to Associate Professor in 2014, and to Full Professor in 2017. The central theme of his research is to explore novel quantum phenomena associated with internal degrees of freedom of electrons such as spin and valley pseudospin for new concept quantum devices, and the current focus is exploring such phenomena in atomically thin 2D materials and their van der Waals heterostructures. He received the Croucher Innovation Award in 2013, and OCPA Achievement in Asia Award (Robert T. Poe Prize) in 2014. He has published 70+ peer-reviewed papers including 25 in Nature series and 15 in Phys. Rev. Lett., with a latest annual citation rate of 3000+ on Google Scholars.