Topological Insulators from Spontaneous Symmetry Breaking Induced by Electron Correlation on Pyrochlore Lattices

Abstract

We study an extended Hubbard model with the nearest-neighbor Coulomb\ninteraction on the pyrochlore lattice at half filling. An interaction-driven\ninsulating phase with nontrivial Z_2 invariants emerges at the Hartree-Fock\nmean-field level in the phase diagram. This topological insulator phase\ncompetes with other ordered states and survives in a parameter region\nsurrounded by a semimetal, antiferromagnetic and charge ordered insulators. The\nsymmetries of these phases are group-theoretically analyzed. We also show that\nthe ferromagnetic interaction enhances the stability of the topological phase.\n