Topological States in Two-Dimensional Su-Schrieffer-Heeger Models

TL;DR

This paper explores the topological phases of 2D SSH models, revealing tunable Dirac points, a novel phase transition, and potential experimental realizations, advancing understanding of topological semimetals and insulators.

Contribution

It introduces two specific 2D SSH models with tunable Dirac points and describes a new topological phase transition leading to diverse topological phases.

Findings

Dirac points are tunable and not fixed at high-symmetry points.

Merging Dirac points induces a novel topological phase transition.

Models can realize weak topological insulator or nodal-line metallic phases.

Abstract

We study the topological properties of the generalized two-dimensional (2D) Su-Schrieffer-Heeger (SSH) models. We show that a pair of Dirac points appear in the Brillouin zone (BZ), consisting a semimetallic phase. Interestingly, the locations of these Dirac points are not pinned to any high-symmetry points of the BZ but tunable by model parameters. Moreover, the merging of two Dirac points undergoes a novel topological phase transition, which leads to either a weak topological insulator or a nodal-line metallic phase. We demonstrate these properties by constructing two specific models, which we referred as type-I and type-II 2D SSH models. The feasible experimental platforms to realize our models are also discussed.