Speaker: Di Xiao, Carmegie Mellon University Title: Chiral charge pumping and circular photogalvanic effect in twisted bilayers Abstract: Twisted bilayers of atomically thin crystals provides a highly tunable platform to investigate structural chirality. In this talk I will discuss two effects related to the chiral structure of twisted bilayer graphene. The first is a chiral topological Thouless pump, in which a sliding motion between the two layers will produce a transverse current. The second is a tunable layer circular photogalvanic effect, in which circular lights can induce an out-of-plane static polarization whose sign is controlled by light chirality. These effects could be useful for developing nanodevices with tunable chiral properties. About the speaker Di Xiao obtained his PhD from the University of Texas at Austin in 2007. He was a staff member at Oak Ridge before joining Carnegie Mellon in 2012. His work is focused on the understanding and prediction of materials properties from the viewpoint of Berry phase and topology. His recent interests involve applying these ideas to 2D materials and spintronics.