Dr. Jun Zhu, Penn State University

"Topological valleytronics in bilayer graphene"

Abstract: The valley pseudospin of 2D hexagonal lattices offers a new electronic degree of freedom to explore many-body ground states and novel paradigms of electronic applications. It is analogous to electron spin however coupling to an electric field offers a powerful control knob that is nimble and application friendly. In this talk, I will describe how we create valley-momentum locked topological 1D channels in Bernal stacked bilayer graphene by electrically generating inverted band structures. This all-electric construction gives us the ability to realize reconfigurable ballistic waveguides and device operations that explicitly explore the valley-momentum locking of the 1D channels. I will show the working of a topological valley valve, which does not require valley-polarized current to operate but relies on the control of topology, and a continuously tunable electron beam splitter that is analogous to the function of a quantum point contact. The realization of these devices requires the development of high-precision lithography on high-quality BN/graphene/BN heterostructures. Time permitting I will touch upon recent development in our lab where new interaction-driven ground states emerge from exploring the valley pseudospin degrees of freedom.

J. Li, K. Wang, K. J. McFaul, Z. Zern, Y. F. Ren, K. Watanabe, T. Taniguchi, Z. H. Qiao, J. Zhu, “Gate-controlled topological conducting channels in bilayer graphene”, Nature Nanotechnology, 11, 1060 (2016)

Jing Li, Rui-Xing Zhang, Zhenxi Yin, Jianxiao Zhang, Kenji Watanabe, Takashi Taniguchi, Chaoxing Liu, Jun Zhu, “A valley valve and electron beam splitter”, Science 362, 1149 (2018)