Edge states of hydrogen terminated monolayer materials: silicene, germanene and stanene ribbons

TL;DR

This paper analyzes the edge state energy dispersion in zigzag silicene, germanene, and stanene nanoribbons, emphasizing the importance of multi-orbital effects and low buckled structures for accurate modeling.

Contribution

It demonstrates that multi-orbital tight-binding models are essential for accurately capturing the nonlinear dispersion of edge states in low-buckled monolayer materials.

Findings

Nonlinear dispersion of edge states due to multi-orbital effects

Single-orbital models yield linear dispersion, missing key features

Multi-orbital models are crucial for understanding tetragen nanoribbons

Abstract

We investigate the energy dispersion of the edge states in zigzag silicene, germanene and stanene nanoribbons with and without hydrogen termination based on a multi-orbital tight-binding model. Since the low buckled structures are crucial for these materials, both the $\pi$ and $\sigma$ orbitals have a strong influence on the edge states, different from the case for graphene nanoribbons. The obtained dispersion of helical edge states is nonlinear, similar to that obtained by first-principles calculations. On the other hand, the dispersion derived from the single-orbital tight-binding model is always linear. Therefore, we find that the non-linearity comes from the multi-orbital effects, and accurate results cannot be obtained by the single-orbital model but can be obtained by the multi-orbital tight-binding model. We show that the multi-orbital model is essential for correctly understanding the dispersion of the edge states in tetragen nanoribbons with a low buckled geometry.