Delocalization of topological surface states by diagonal disorder in nodal loop semimetals

TL;DR

This paper investigates how diagonal disorder affects the topological surface states in Weyl nodal loop semimetals, showing that disorder causes surface state delocalization and eventual hybridization with bulk states at a critical disorder level.

Contribution

It demonstrates the impact of Anderson diagonal disorder on drumhead surface states, revealing their transition from localized to extended states as disorder increases.

Findings

Surface states exhibit algebraic decay into the bulk under disorder.

Disorder broadens the low energy surface state density.

Surface states hybridize with bulk states beyond a critical disorder Wc.

Abstract

The effect of Anderson diagonal disorder on the topological surface (``drumhead'') states of a Weyl nodal loop semimetal is addressed. Since diagonal disorder breaks chiral symmetry, a winding number cannot be defined. Seen as a perturbation, the weak random potential mixes the clean exponentially localized drumhead states of the semimetal, thereby producing two effects: (i) the algebraic decay of the surface states into the bulk; (ii) a broadening of the low energy density of surface states of the open system due to degeneracy lifting. This behavior persists with increasing disorder, up to the bulk semimetal-to-metal transition at the critical disorder $W_{c}$. Above $W_{c}$, the surface states hybridize with bulk states and become extended into the bulk.