The weak side of strong topological insulators

TL;DR

This paper explores how weak indices in strong topological insulators lead to topologically protected states along lattice line defects, affecting surface transport and spectral properties.

Contribution

It reveals the impact of weak indices on defect states in strong topological insulators and their influence on surface transport phenomena.

Findings

Line defects host topologically protected helical states.

These states can suppress or enhance surface conductivity.

Defect phases determine spectral gap or density of states.

Abstract

Strong topological insulators may have nonzero weak indices. The nonzero weak indices allow for the existence of topologically protected helical states along line defects of the lattice. If the lattice admits line defects that connect opposite surfaces of a slab of such a "weak-and-strong" topological insulator, these states effectively connect the surface states at opposite surfaces. Depending on the phases accumulated along the dislocation lines, this connection results in a suppression of in-plane transport and the opening of a spectral gap or in an enhanced density of states and an increased conductivity.