High Surface Conductivity of Fermi Arc Electrons in Weyl semimetals

TL;DR

This paper investigates the surface conductivity of Weyl semimetals, revealing that Fermi arc shape and disorder significantly influence transport properties, with straight arcs showing remarkable disorder tolerance and high conductivity.

Contribution

It demonstrates how Fermi arc curvature affects electron-phonon scattering and surface conductivity, and shows that straight Fermi arcs are highly resistant to surface disorder in Weyl semimetals.

Findings

Surface conductivity depends on Fermi arc curvature.

Straight Fermi arcs exhibit high disorder tolerance.

Simulations on TaAs confirm topological surface state robustness.

Abstract

Weyl semimetals (WSMs), a new type of topological condensed matter, are currently attracting great interest due to their unusual electronic states and intriguing transport properties such as chiral anomaly induced negative magnetoresistance, a semi--quantized anomalous Hall effect and the debated chiral magnetic effect. These systems are close cousins of topological insulators (TIs) which are known for their disorder tolerant surface states. Similarly, WSMs exhibit unique topologically protected Fermi arcs surface states. Here we analyze electron--phonon scattering, a primary source of resistivity in metals at finite temperatures, as a function of the shape of the Fermi arc where we find that the impact on surface transport is significantly dependent on the arc curvature and disappears in the limit of a straight arc. Next, we discuss the effect of strong surface disorder on the resistivity by numerically simulating a tight binding model with the presence of quenched surface vacancies using the Coherent Potential Approximation (CPA) and Kubo--Greenwood formalism. We find that the limit of a straight arc geometry is remarkably disorder tolerant, producing surface conductivity that is a factor of 50 larger of a comparable set up with surface states of TI. Finally, a simulation of the effects of surface vacancies on TaAs is presented, illustrating the disorder tolerance of the topological surface states in a recently discovered WSM material.