Phase diagram and topological phases in the triangular lattice Kitaev-Hubbard model

TL;DR

This paper explores the phase diagram of a half-filled Hubbard model on a triangular lattice with Kitaev-like hopping, revealing multiple phases including magnetic orders, a nonmagnetic insulator, and a topological Chern insulator, highlighting the interplay of topology and strong correlations.

Contribution

It introduces a comprehensive phase diagram for the Kitaev-Hubbard model on a triangular lattice, identifying novel phases and transitions using variational cluster and slave-rotor methods.

Findings

Identification of five distinct phases including a Chern insulator and a nonmagnetic insulator.

Characterization of phase transitions via charge gap changes.

Proposal of a gapless Mott insulator with a spinon Fermi surface.

Abstract

We study the half-filled Hubbard model on the triangular lattice with spin-dependent Kitaev-like hopping. Using the variational cluster approach, we identify five phases: a metallic phase, a non-coplanar chiral magnetic order, a $120^\circ$ magnetic order, a nonmagnetic insulator (NMI), and an interacting Chern insulator (CI) with a nonzero Chern number. The transition from CI to NMI is characterized by the change of the charge gap from an indirect band gap to a direct Mott gap. Based on the slave-rotor mean-field theory, the NMI phase is further suggested to be a gapless Mott insulator with a spinon Fermi surface or a fractionalized CI with nontrivial spinon topology, depending on the strength of Kitaev-like hopping. Our work highlights the rising field that interesting phases emerge from the interplay of band topology and Mott physics.