Magnetic Island Induced Electron Scattering on the Surface of 3D Topological Insulators

We investigate theoretically the scattering of electrons impinging on a circular magnetically gapped region on the surface of a three-dimensional time-reversal-invariant topological insulator (3D TI). This work is motivated by the recent surge in theoretical and experimental interest in the interplay between topology and magnetism, as it provides insight on electron transport in TI surface states with local time-reversal symmetry breaking. We work in the limit of a massless exterior region (no magnetization), to understand the interface between a gapless region and a Chern number ½ region. Based on calculations of current flow in this system, we predict that an anomalous Hall effect can be generated on the surface of a 3D TI decorated by magnetic islands.