Topological insulators and topological superconductors

Who:  Xiaoliang Qi - (Stanford)
Where:  Smith Seminar Room (1080 PRB)
When:  Monday, November 23, 2009 at 11:30
Type:  Condensed Matter Theory Seminar

Description: Topological insulators are new states of matter which are gapped in the bulk but have gapless, topologically protected surface states. In recent years, time reversal invariant topological insulators have been discovered in HgTe quantum wells and bulk crystals Bi2Se3, Bi2Te3 and Bi1-xSbx alloy. Topological insulators have many unusual physical properties. For example, an image “magnetic monopole” is induced by a point charge near the surface of the topological insulator. If in addition an antiferromagnetic order is established in the topological insulator phase, a topological coupling is induced between spin-wave excitations and photons, leading to the design of a tunable optical modulator.

Topological superconductors are cousins of topological insulators with superconducting gap in the bulk but robust gapless Bogoliubov quasiparticles on the boundary. Topological superconductors are important candidates for building quantum computers, but no topological superconductor has been discovered in three dimensions. We propose a simple and generic criterion for topological superconductors based on Fermi surface properties, which can be used in the search of topological superconductors.