Spectroscopic signatures of Weyl semimetals beyond photoemission
Abstract: Weyl semimetals are a newly discovered class of three-dimensional topological materials, whose distinctive spectral properties have been recently visualized using angle-resolved photoemission. In this talk I will present how the defining topological features of Weyl semimetals — open Fermi surfaces at the boundary (Fermi arcs) and linear band touchings in the bulk (Weyl nodes) — are captured by two alternative spectroscopic probes of matter that measure exclusively either the surface or the bulk, namely, scanning tunneling spectroscopy (STS) and resonant inelastic x-ray scattering (RIXS). The quasiparticle interference (QPI) pattern obtained in STS of Weyl semimetals contains characteristic shapes that can be unequivocally associated with the presence of Fermi arcs at the surface. I will discuss the universal QPI signatures of Fermi arcs and their experimental observation. RIXS is a powerful core-level spectroscopy that can resolve charge, spin and orbital degrees of freedom in the bulk. I will demonstrate how the unique sensitivity of this method can be employed to measure the absolute topological charge of a Weyl node.