2010/03/31 by Wang-Kong Tse, A. H. MacDonald
Physics and Astronomy · #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevlett.105.057401
published as Phys. Rev. Lett. 105, 057401 (2010) [Editor's suggestion]. See also accompanying Viewpoint article · 5 pages, 4 figures
arxiv created 2010/07/27 · arxiv updated 2015/05/18
Topological insulators can exhibit strong magnetoelectric effects when their time-reversal symmetry is broken. In this Letter we consider the magneto-optical Kerr and Faraday effects of a topological insulator thin film weakly exchange-coupled to a ferromagnet. We find that its Faraday rotation has a universal value at low-frequencies, θF = tan-1 α where α is the vacuum fine structure constant, and that it has a giant Kerr rotation θK = π/2. These properties follow from a delicate interplay between thin-film cavity confinement and the surface Hall conductivity of a topological insulator's helical quasiparticles.