Impurity-induced states on the surface of three-dimensional topological insulators

We calculate the modification of the local electronic structure caused by a single local impurity on the surface of a three-dimensional topological insulator. We find that the local density of states around the Dirac point of the electronic spectrum at the surface is significantly disrupted near the impurity by the creation of low-energy resonance state(s)---however, this is not sufficient to (locally) destroy the Dirac point. We also calculate the nontrivial spin textures created near the magnetic impurities and discover anisotropic Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling between them.