Topology of chalcogen chains

TL;DR

This paper explores the topological properties of helical chalcogen atomic chains, revealing their non-trivial topology protected by crystalline symmetry and describing edge states with orbital polarization.

Contribution

It introduces a realistic model including spin-orbit interaction and a simplified orbital chain model to analyze topological invariants in chalcogen chains.

Findings

Chalcogen chains are topologically non-trivial with crystalline symmetry protection.

Edge states are orbitally polarized with density peaks at the edges.

A simplified model decomposes into three orbital chains for topological analysis.

Abstract

We investigate the topological properties of the helical atomic chains occurring in elemental selenium and tellurium. We postulate a realistic model that includes spin-orbit interaction and show this to be topologically non-trivial, with a topological invariant protected by a crystalline symmetry. We describe the end-states, which are orbitally polarized, with an orbital density modulation strongly peaked at the edge. Furthermore, we propose a simplified model that decomposes into three orbital chains, allowing us to define a topological invariant protected by a crystalline symmetry. We contrast this result with recent observations made for the orbital Su-Schrieffer-Heeger model containing a $p$-orbital zigzag chain.