Fermi-arc diversity on surface terminations of the magnetic Weyl semimetal Co ₃ Sn ₂ S ₂

Abstract

contributionsBulk-surface correspondence in Weyl semimetals assures the formation of topological "Fermi-arc" surface bands whose existence is guaranteed by bulk Weyl nodes. By investigating three distinct surface terminations of the ferromagnetic semimetal Co 3 Sn 2 S 2 we verify spectroscopically its classification as a time reversal symmetry broken Weyl semimetal. We show that the distinct surface potentials imposed by three different terminations modify the Fermi-arc contour and Weyl node connectivity. On the Sn surface we identify intra-Brillouin zone Weyl node connectivity of Fermi-arcs, while on Co termination the connectivity is across adjacent Brillouin zones. On the S surface Fermiarcs overlap with non-topological bulk and surface states that ambiguate their connectivity and obscure their exact identification. By these we resolve the topologically protected electronic properties of a Weyl semimetal and its unprotected ones that can be manipulated and engineered.Topological semimetals lend a unique experimental opportunity to investigate both bulk and surface topological properties by probing their topological surface states (1-6). Unlike in gapped topological system the dispersion of the topological surface bands is intimately correlated with the topological bulk bands dispersion (7,8). Prime examples are Weyl and Dirac semimetals whose nontrivial topological properties arise from the existence of nondegenerate band-touching points, termed Weyl nodes, in the electronic bulk band structure. Bulk Weyl nodes are formed under broken inversion or time reversal symmetry. They exhibit certain chirality and give rise to the formation of open-contour "Fermi-arc" surface bands that emanate from a certain Weyl node and terminate at another with opposite chirality within the surface two dimensional momentum space. Due to this surface-bulk correspondence, the dispersion of the Fermi-arcs reflects the

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