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. 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 “pseudospin” 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 “puddles”. 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

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