Impurity screening and stability of Fermi arcs against Coulomband magnetic scattering in a Weyl monopnictide

TL;DR

This study investigates the stability and screening of Fermi arcs in Weyl semimetals TaAs with Mn doping, revealing suppressed scattering and challenging previous interpretations of Fermi arc interference signals.

Contribution

It provides the first direct quasiparticle interference evidence that Fermi arcs are robust against Coulomb and magnetic scattering in Weyl semimetals.

Findings

Impurities are effectively screened in Weyl semimetals.

Three new short scattering vectors linked to trivial states.

Fermi arcs show strong suppression of intra- and inter-arc scattering.

Abstract

We present a quasiparticle interference study of clean and Mn surface-doped TaAs, a prototypical Weyl semimetal, to test the screening properties as well as the stability of Fermi arcs against Coulomb and magnetic scattering. Contrary to topological insulators, the impurities are effectively screened in Weyl semimetals. The adatoms significantly enhance the strength of the signal such that theoretical predictions on the potential impact of Fermi arcs can be unambiguously scrutinized. Our analysis reveals the existence of three extremely short, previously unknown scattering vectors. Comparison with theory traces them back to scattering events between large parallel segments of spin-split trivial states, strongly limiting their coherence. In sharp contrast to previous work [R. Batabyal et al., Sci. Adv. 2, e1600709 (2016)], where similar but weaker subtle modulations were interpreted as evidence of quasiparticle interference originating from Femi arcs, we can safely exclude this being the case. Overall, our results indicate that intra- as well as inter-Fermi arc scattering are strongly suppressed and may explain why-in spite of their complex multiband structure-transport measurements show signatures of topological states in Weyl monopnictides.