Kagome edge states under lattice termination, spin-orbit coupling, and magnetic order

TL;DR

This paper investigates how lattice termination, spin-orbit coupling, and magnetic order influence edge states in a kagome lattice, revealing conditions for topological phases and edge state robustness.

Contribution

It provides a comprehensive analysis of edge state behavior in kagome lattices under various physical effects, highlighting the tunability of topological phases.

Findings

Edge states are highly sensitive to boundary geometry in the pristine limit.

Kane-Mele spin-orbit coupling induces a robust $ ext{Z}_2$ topological insulator phase.

Zeeman and Rashba couplings lead to Chern insulating phases with chiral edge modes.

Abstract

We study the edge state properties of a two-dimensional kagome lattice using a tight-binding approach, focusing on the role of lattice termination, spin-orbit coupling, and magnetic order. In the pristine limit, we show that the existence of localized edge states is highly sensitive to boundary geometry, with certain terminations completely suppressing edge modes. Kane-Mele spin-orbit coupling opens a bulk gap and stabilizes topologically protected helical edge states, yielding a robust $\mathbb{Z}_2$ insulating phase that is insensitive to termination details. In contrast, the combined effect of a Zeeman field and Rashba spin-orbit coupling drives the system into Chern insulating phases, with Chern numbers consistent with the number of chiral edge modes. We further demonstrate that non-coplanar magnetic textures generate multiple Chern phases through finite scalar spin chirality, with Kane-Mele coupling strongly tuning the topological gaps. Our results provide important insights into the tunability of edge states in the kagome lattice, which can be key to designing materials with novel electronic properties and topological phases.