Speaker: Michael S. Fuhrer
Abstract Details: The three dimensional strong topological insulator (STI) is a new phase of electronic matter which is distinct from ordinary insulators in that it supports on its surface a conducting two-dimensional surface state whose existence is guaranteed by topology. I will discuss experiments on the STI material Bi2Se3, which has a bulk bandgap of ~300 meV, much greater than room temperature, and a single topological surface state whose electrons obey a massless Dirac equation describing chiral particles with spin-momentum coupling.Â Parallels will be drawn between the conducting properties of the STI surface state and graphene, whose electrons also obey a two-dimensional Dirac equation, with coupling of momentum to an orbital â€œpseudospinâ€ degree of freedom. In particular, the minimum conductivity as the Fermi energy approaches the Dirac point in both systems is determined by long-range disorder which breaks the system into electron and hole â€œpuddlesâ€. Scattering by acoustic phonons give a temperature-dependent resistance which is independent of Fermi energy. The chiral STI surface state of Bi2Se3 shows perfect weak anti-localization, difficult to observe in graphene due to imperfect chirality of the carriers.
About the Speaker: School of Physics, Monash University, Clayton, Victoria 3800, Australia and
Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742-4111, USA