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

TL;DR

This paper demonstrates that electron correlations on pyrochlore lattices can induce a topological insulator phase through spontaneous symmetry breaking, expanding understanding of correlation-driven topological states.

Contribution

It introduces a new interaction-driven topological insulator phase in an extended Hubbard model on pyrochlore lattices, analyzed via mean-field theory and symmetry considerations.

Findings

Interaction-driven topological insulator phase identified

Phase survives amid competing orders like semimetal and magnetic states

Ferromagnetic interactions enhance topological phase stability

Abstract

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