Phase transitions of the Kane-Mele-Hubbard model with a long-range hopping

TL;DR

This paper investigates phase transitions in an extended Kane-Mele-Hubbard model with long-range hopping, analyzing topological, Mott, and magnetic transitions using analytical and mean-field methods, and provides comprehensive phase diagrams.

Contribution

It introduces a four-lattice-constant range hopping into the Kane-Mele-Hubbard model and analyzes its effects on topological and correlated phases.

Findings

Critical long-range hopping strength for topological transition is independent of spin-orbit coupling.

Below the Mott transition, the system is a correlated quantum spin Hall state; above it, a topological Mott insulator.

Phase diagrams are mapped out showing the influence of interactions and spin-orbit coupling.

Abstract

The interacting Kane-Mele model with a long-range hopping is studied using analytical method. The original Kane-Mele model is defined on a honeycomb lattice. In the work, we introduce a four-lattice-constant range hopping and the on-site Hubbard interaction into the model and keep its lattice structure unchanged. From the single-particle energy spectrum, we obtain the critical strength of the long-range hopping $t_L$ at which the topological transition occurs in the non-interacting limit of the model and our results show that it is independent of the spin-orbit coupling. After introducing the Hubbard interaction, we investigate the Mott transition and the magnetic transition of the generalized strongly correlated Kane-Mele model using the slave-rotor mean field theory and Hartree-Fock mean field theory respectively. In the small long-range hopping region, it is a correlated quantum spin Hall state below the Mott transition, while a topological Mott insulator above the Mott transition. By comparing the energy band of spin degree of freedom with the one of electrons in non-interacting limit, we find a condition for the $t_L$-driven topological transition. Under the condition, critical values of $t_L$ at which the topological transition occurs are obtain numerically from seven self-consistency equations in both regions below and above the Mott transition. Influences of the interaction and the spin-orbit coupling on the topological transition are discussed in this work. Finally, we show complete phase diagrams of the generalized interacting topological model at some strength of spin-orbital coupling.