Evidence of robust edge mode in magnetic Weyl semimetal Co3Sn2S2

Ferromagnetic Weyl semimetal Co3Sn2S2 belongs to the family of magnetic topological materials where time-reversal symmetry is spontaneously broken. We use scanning tunneling microscopy and spectroscopy to study its topological nature by measuring robust boundary responses. Upon studying several clean step edges we have identified the existence of an edge mode within a formerly unidentified energy window. With the support of ab initio calculation, we are able to relate this edge mode to a new set of Weyl nodes within a corresponding energy interval. Furthermore, we have observed the systematic evolution of the edge mode from a state bound to a single vacancy through a growing cluster of vacancies. This observation demonstrates the deep relation between defect states and Fermi arc states at extended crystallographic boundaries, both governed by the topological semimetallic nature of the bulk.