Quantum spin Hall effect in a two-orbital model on a honeycomb lattice

TL;DR

This paper explores the quantum spin Hall effect in a two-orbital honeycomb lattice model, revealing three distinct topological phases characterized by quantized spin Hall conductivities and analyzing phase boundaries with Dirac nodes.

Contribution

It introduces a new two-orbital model on a honeycomb lattice exhibiting multiple topological phases and analytically determines phase boundaries and their relation to spin-orbit coupling.

Findings

Identification of three topologically different insulating phases.

Analytical determination of phase boundaries with Dirac nodes.

Discussion of the model's relation to the Kane-Mele model and magnetoelectric effects.

Abstract

The spin Hall effect is investigated in a two-orbital tight-binding model on a honeycomb lattice. We show that the model exhibits three topologically-different insulating phases at half filling, which are distinguished by different quantized values of the spin Hall conductivity. We analytically determine the phase boundaries, where the valence and conduction bands touch with each other with forming the Dirac nodes at the Fermi level. The results are discussed in terms of the effective antisymmetric spin-orbit coupling. The relation to the Kane-Mele model and implications for a magnetoelectric effect are also discussed.