Condensed Matter Seminar

Joel Moore
University of California, Berkley & LBNL

Thursday, September 28, 2006
1:00 pm in SPL 52

Spin transport and the topological insulator

Abstract: Spin transport in solids differs from charge transport in some ways that are obvious and in some ways that are still being understood. This talk first reviews experiments and theory on spin drag as an example of how, in a Fermi liquid, electron-electron interactions are much more relevant for spin transport than for charge transport. The dissipationless spin Hall effect proposed by Kane and Mele for graphene is then discussed and shown to result from a topological classification of band insulators that is similar to the Chern number picture of the integer quantum Hall effect. In two dimensions, each band pair of a time-reversal-invariant fermion system carries a Z2 index, and a band insulator is either an "ordinary" or "topological" insulator according to the sum of these indices. The topological insulator generically shows a robust spin Hall effect. Generalizations to 3D systems, which have 16 different types of band insulator, and weak interactions are discussed.

This work involved collaborations with Leon Balents, Cenke Xu, and the Orenstein and Awschalom experimental groups.