Edge modes in zigzag and armchair ribbons of monolayer MoS$_2$

TL;DR

This paper investigates the electronic and topological properties of monolayer MoS$_2$ nanoribbons, revealing edge modes in zigzag ribbons linked to topological features and valley Hall insulator behavior, with boundary conditions affecting armchair edges.

Contribution

It provides a detailed analysis of edge modes in MoS$_2$ nanoribbons using tight-binding and low-energy models, highlighting their topological origin and the effects of boundary conditions.

Findings

Mid-gap edge mode in zigzag MoS$_2$ ribbons

Edge modes are topologically derived from bulk properties

Boundary conditions induce a gap in armchair edge modes

Abstract

We explore the electronic structure, orbital character and topological aspect of a monolayer MoS$_2$ nanoribbon using tight-binding (TB) and low-energy (${\bm k}\cdot{\bm p} $) models. We obtain a mid-gap edge mode in the zigzag ribbon of monolayer MoS$_2$, which can be traced back to the topological properties of the bulk band structure. Monolayer MoS$_2$ can be considered as a valley Hall insulator. The boundary conditions at armchair edges mix the valleys on the edges, and a gap is induced in the edge modes. The spin-orbit coupling in the valence band reduces the hybridization of the bulk states.