Topologically-protected metallic states induced by a one-dimensional extended defect in a 2D topological insulator

TL;DR

This study demonstrates through ab initio calculations that a one-dimensional extended defect in a 2D topological insulator can induce topologically-protected metallic states, revealing a new way to engineer edge states in such materials.

Contribution

It introduces a novel mechanism for creating topologically-protected metallic states via a specific extended defect in a 2D topological insulator, supported by first-principles calculations.

Findings

Extended defect induces two pairs of Dirac-fermion states.

States are localized along the defect core.

Interactions between states are screened due to trivial topology.

Abstract

We report ab initio calculations showing that a single one-dimensional extended defect can originate topologically-protected metallic states in the bulk of two-dimensional topological insulators. We find that a narrow extended defect composed of periodic units consisting of one octogonal and two pentagonal rings embedded in the hexagonal bulk of a bismuth bilayer introduces two pairs of one-dimensional Dirac-fermion states with opposite spin-momentum locking. Although both Dirac pairs are localized along the extended-defect core, their interactions are screened due to the trivial topological nature of the extended defect.