Signatures of Weyl semimetals in quasiparticle interference

TL;DR

This paper demonstrates how quasiparticle interference patterns, observable via scanning tunneling spectroscopy, can reveal topological features of Weyl semimetals, including Fermi arcs and line nodes, using an exact Green's function approach.

Contribution

It introduces an exact Green's function formalism to analyze QPI signatures in Weyl semimetals, accounting for surface effects and perturbations, advancing understanding of topological surface states.

Findings

QPI patterns depend on surface orientation and perturbations.

Fermi arcs may or may not appear in QPI, influenced by interference effects.

Joint-density-of-states approach is inadequate for describing QPI extinction.

Abstract

Impurities act as in situ probes of nontrivial electronic structure, causing real-space modulations in the density of states detected by scanning tunneling spectroscopy on the sample surface. We show that distinctive topological features of Weyl semimetals can be revealed in the Fourier transform of this map, interpreted in terms of quasiparticle interference (QPI). We develop an exact Green's function formalism and apply it to generalized models of Weyl semimetals with an explicit surface. The type of perturbation lifting the Dirac node degeneracy to produce the three-dimensional bulk Weyl phase determines the specific QPI signatures appearing on the surface. QPI Fermi arcs may or may not appear, depending on the relative surface orientation and quantum interference effects. Line nodes give rise to tube projections of width controlled by the bias voltage. We consider the effect of crystal warping, distinguishing dispersive arclike features from true Fermi arcs. Finally, we demonstrate that the commonly used joint-density-of-states approach fails qualitatively, and cannot describe QPI extinction.