The discovery of Weyl semimetals represents a significant advance intopological band theory. They paradigmatically enlarged the classification oftopological materials to gapless systems while simultaneously providingexperimental evidence for the long-sought Weyl fermions. Beyond fundamentalrelevance, their high mobility, strong magnetoresistance, and the possibleexistence of even more exotic effects, such as the chiral anomaly, make Weylsemimetals a promising platform to develop radically new technology. Fullyexploiting their potential requires going beyond the mere identification ofmaterials and calls for a detailed characterization of their functionalresponse, which is severely complicated by the coexistence of surface- andbulk-derived topologically protected quasiparticles, i.e., Fermi arcs and Weylpoints, respectively. Here, we focus on the type-II Weyl semimetal class wherewe find a stoichiometry-dependent phase transition from a trivial to anon-trivial regime. By exploring the two extreme cases of the phase diagram, wedemonstrate the existence of a universal response of both surface and bulkstates to perturbations. We show that quasi-particle interference patternsoriginate from scattering events among surface arcs. Analysis reveals thattopologically non-trivial contributions are strongly suppressed by spintexture. We also show that scattering at localized impurities generatedefect-induced quasiparticles sitting close to the Weyl point energy. Thesegive rise to strong peaks in the local density of states, which lift the Weylnode significantly altering the pristine low-energy Weyl spectrum. Visualizingthe microscopic response to scattering has important consequences forunderstanding the unusual transport properties of this class of materials.Overall, our observations provide a unifying picture of the Weyl phase diagram.
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