Surface plasmons and topological insulators

We study surface plasmons localized on interfaces between topologically trivial and topologically nontrivial time reversal invariant materials in three dimensions. For the interface between ametal and a topological insulator the magnetic polarization of the surface plasmon is rotated out of the plane of the interface; this effect should be experimentally observable by exciting the surface plasmon with polarized light. More interestingly, we argue that the same effect also is realized on the interface between vacuum and a doped topological insulator with nonvanishing bulk carrier density.