Do the surface Fermi arcs in Weyl semimetals survive disorder?

TL;DR

This study investigates the impact of disorder on Weyl Fermi-arc surface states, revealing they are not topologically protected but the surface chiral velocity remains robust even in strong disorder.

Contribution

It provides numerical evidence that Weyl Fermi-arcs lose their topological protection under disorder, while the surface chiral velocity persists.

Findings

Fermi-arc surface states hybridize with bulk states and lose their surface-bound character.

Surface chiral velocity remains robust and survives strong disorder.

Weyl Fermi-arcs are not topologically protected from disorder.

Abstract

We theoretically study the topological robustness of the surface physics induced by Weyl Fermi-arc surface states in the presence of short-ranged quenched disorder and surface-bulk hybridization. This is investigated with numerically exact calculations on a lattice model exhibiting Weyl Fermi-arcs. We find that the Fermi-arc surface states, in addition to having a finite lifetime from disorder broadening, hybridize with nonperturbative bulk rare states making them no longer bound to the surface (i.e. they lose their purely surface spectral character). Thus, we provide strong numerical evidence that the Weyl Fermi-arcs are not topologically protected from disorder. Nonetheless, the surface chiral velocity is robust and survives in the presence of strong disorder, persisting all the way to the Anderson-localized phase by forming localized current loops that live within the localization length of the surface. Thus, the Weyl semimetal is not topologically robust to the presence of disorder, but the surface chiral velocity is.