Quantum anomalous Hall state from spatially decaying interactions on the decorated honeycomb lattice

Topological phases typically encode topology at the level of the single-particle band structure. But a remarkable class of models shows that quantum anomalous Hall effects can be driven exclusively by interactions, while the parent noninteracting 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 a model of spinless fermions on a decorated honeycomb lattice. Using complementary methods, mean-field theory and exact diagonalization, we find a robust quantum anomalous Hall phase arising from spatially decaying interactions. Our finding indicates that the quantum anomalous Hall effect driven entirely by interactions is a surprisingly robust and realistic phenomenon.