Stephan Rachel, Yale University
We discuss the effect of electron-electron interactions in a two-dimensional topological insulator (as realized by the Kane-Mele model on the honeycomb lattice). The topological insulator phase turns out to be stable up to quite large interactions. For very strong electron-electron interactions, the system is magnetically ordered and we are able to derive an effective spin model. For intermediate interactions, the possible existence of more exotic phases such as spin liquids, topological Mott insulators, and even topologically ordered phases is discussed. In addition, we show that lattice anisotropy and its combination with electron-electron interactions results in a rich phase diagram.