Interaction-driven topological insulators on the kagome and the decorated honeycomb lattices

TL;DR

This paper investigates how electron interactions can induce topological insulating phases in kagome and decorated honeycomb lattices, revealing potential for realizing topological insulators without strong spin-orbit coupling.

Contribution

It demonstrates the existence of interaction-driven topological insulators in specific lattice models using mean-field theory, expanding the understanding of topological phases beyond spin-orbit coupling effects.

Findings

Interaction-driven topological phases exist at certain fillings.

Phase diagrams show competition between topological and ordered states.

Topological insulators may be realized with minimal spin-orbit coupling.

Abstract

We study the spinless and spinful extended Hubbard models with repulsive interactions on the kagome and the decorated honeycomb ("star") lattice. Using Hartree-Fock mean-field theory, we show that interaction-driven insulating phases with non-trivial topological invariants (Chern number or $Z_2$ invariant) exist for an experimentally reasonable range of parameters. These phases occur at filling fractions which involve either Dirac points or quadratic band crossing points in the non-interacting limit. We present comprehensive mean-field phase diagrams for these lattices and discuss the competition between topologically non-trivial phases and numerous other ordered states, including various charge, spin, and bond orderings. Our results suggest that $Z_2$ topological insulators should be found in a number of systems with either little or no intrinsic spin-orbit coupling.