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 electron beam irradiation and electrostatic gating, we further show a dramatic enhancement in the carrier mobility as we continuously move the Fermi level from the valence band into the bulk band gap. This large mobility enhancement is consistent with the suppressed backscattering expected for surface Dirac fermions in TIs. I will also present other transport results such as the weak antilocalization and quantum oscillations in those devices.
Coffee and tea will be served 20 minutes prior to the seminar.