Dr. Pouyan Ghaemi Department of Physics University of Illinois, Urbana _____________________________________________________________ DARPA MESO Seminar ***Tuesday, November 15, 2011 2:00 PM - 3:00 PM, Room 206, MRGN*** Enhanced thermoelectric performance in Topological insulator thin films Several small-bandgap semiconductors are now known to have protected metallic surface states as a consequence of the topology of the bulk electron wavefunctions. The known "topological insulators" with this behavior include the important thermoelectric materials Bi22Te3 and Bi2Se3, whose surfaces are observed in photoemission experiments to have an unusual electronic structure with a single Dirac cone. We study in-plane (i.e., horizontal) transport in thin films made of these materials. The surface states from top and bottom surfaces hybridize, and conventional diffusive transport predicts that the tunable hybridization-induced band gap leads to increased thermoelectric performance at low temperatures. Beyond simple diffusive transport, the conductivity shows a crossover from the spin-orbit induced anti-localization at a single surface to ordinary localization.