Abstract:
Bi2Se3 is predicted to be a 3D topological insulator (TI) with a large band gap and a single Dirac cone. Although surface sensitive spectroscopy has revealed the nature of the surface Dirac fermion states in Be2Se3, due to the coexistence of the bulk and surface states, transport evidence of the surface Dirac fermion states has been elusive. In this talk, I will present our effort to tune the Fermi level position in both bulk Bi2Se3 crystals and nanodevices. First we demonstrate the insulating bulk state in nanodevices which is a pre-requisite for transport studies. By electrostatic gating, we further show dramatic enhancement in the carrier mobility as we move the Fermi level from the valence band into the bulk band gap. This large mobility enhancement is consistent with the suppressed backscattering for surface Dirac fermions in TIs.

Biosketch:
Jing Shi received his Ph.D. in Physics in 1994 from the University of Illinois at Urbana-Champaign. He did his postdoctoral research in the University of California at Santa Barbara. He had worked as a Senior Staff Scientist at Motorola Labs before joining the faculty of the University of Utah’s Physics Department in 1999. Since 2005, he has been a professor at the University of California, Riverside. His research interest includes nanoscale magnetism and spintronics, graphene, and more recently topological insulators.