Department of Physics, University of Texas, Austin, Texas 78712, USA.
Phys Rev Lett. 2010 Jul 30;105(5):057401. doi: 10.1103/PhysRevLett.105.057401. Epub 2010 Jul 26.
Topological insulators can exhibit strong magneto-electric 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.
拓扑绝缘体在时间反演对称性被破坏时会表现出强烈的磁电效应。在这封信中，我们考虑了弱交换耦合到铁磁体的拓扑绝缘体薄膜的磁光克尔和法拉第效应。我们发现，它的法拉第旋转在低频时具有一个通用的值θF=tan(-1)α，其中α是真空精细结构常数，并且它具有巨大的克尔旋转θK=π/2。这些特性源于薄膜腔限制和拓扑绝缘体螺旋准粒子的表面霍尔电导率之间的微妙相互作用。
