Signatures of a topological Weyl loop in CoSnS
arXiv:2005.02400
Abstract
The search for novel topological phases of matter in quantum magnets has emerged as a frontier of condensed matter physics. Here we use state-of-the-art angle-resolved photoemission spectroscopy (ARPES) to investigate single crystals of CoSnS in its ferromagnetic phase. We report for the first time signatures of a topological Weyl loop. From fundamental symmetry considerations, this magnetic Weyl loop is expected to be gapless if spin-orbit coupling (SOC) is strictly zero but gapped, with possible Weyl points, under finite SOC. We point out that high-resolution ARPES results to date cannot unambiguously resolve the SOC gap anywhere along the Weyl loop, leaving open the possibility that CoSnS hosts zero Weyl points or some non-zero number of Weyl points. On the surface of our samples, we further observe a possible Fermi arc, but we are unable to clearly verify its topological nature using the established counting criteria. As a result, we argue that from the point of view of photoemission spectroscopy the presence of Weyl points and Fermi arcs in CoSnS remains ambiguous. Our results have implications for ongoing investigations of CoSnS and other topological magnets.
arXiv commentCo3Sn2S2; comments welcome. Manuscript unchanged, updated comment: companion paper to arXiv:2105.14034, which is published as Phys. Rev. Lett. 127, 256403 (2021) at https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.256403
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