Topological phase transitions on the square-hexagon lattice

School of Science, Henan Institute of Technology - 453003 XinXiang, China

^(a) gxwang@hait.edu.cn (corresponding author)

Received: 11 October 2021
Accepted: 1 February 2022

Abstract

We study the tight-binding model of the square-hexagon lattice, which supports two kinds of nearest-neighbor hoppings and spin-orbit couplings. Based on the parity criterion and Fukui-Hatsugai method, the topological properties are investigated. In the presence of spin-orbit coupling, topological phase transition between topological semimetal and normal band insulator can be realized. The phase diagrams as a function of the spin-orbit couplings, and , are presented. Also, the effects of the Rashba spin-orbit coupling and staggered potential are discussed. We find that the Rashba spin-orbit coupling can drive the square-hexagon lattice into topological nontrivial phase at 1/5 and 2/5 filling fraction. The helical edge states are given numerically to confirm the topological property of square-hexagon lattice. Our results enlarge the number of two-dimensional lattices which have only a simple cubic symmetry and can support topological nontrivial phase.