Topological Mott Insulators in Certain Frustrated Lattices

Topological phases typically encode topology at the level of the single particle band structure. But a remarkable new class of models shows that quantum anomalous Hall effects can be driven exclusively by interactions, while the parent non-interacting band structure is topologically trivial. Unfortunately, these models have so far relied on interactions that do not spatially decay and are therefore unphysical. We study two-dimensional models of spinless fermions on frustrated lattices (decorated honeycomb and kagome). Using complementary methods, mean-field theory and exact diagonalization, we find a robust quantum anomalous Hall phase arising from spatially decaying interactions, including a screened Coulomb interaction. Our findings indicate that interactions alone can, in principle, drive topologically trivial single-particle states into topological phases in certain frustrated lattice models. These models in turn offer a starting point to engineer the quantum anomalous Hall phases in two-dimensional ferromagnets.