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Prediction of Double-Weyl Nodes in the Iron-based Superconductor CaKFe<sub>4</sub>As<sub>4</sub>

ORAL

Abstract

By combining group-theoretical symmetry analysis, low-energy model calculations, and ab-initio simulations, we predict the presence of a pair of magnetic-field induced Weyl nodes close to the Fermi level in the iron-based superconductor CaKFe4As4. Contrary to other topological phenomena proposed in iron-based superconductors, this one originates entirely from the 3d Fe states. As opposed to conventional Weyl fermions, the Weyl states realized in this material carry a topological charge of ±2, making CaKFe4As4 a candiate for a double-Weyl semimetal, when appropriately tuned or doped. The higher-order topological charge is stabilized by the fourfold rotational symmetry of the M-A line, which leads to a quadratic dispersion of the Weyl nodes in the kx-ky plane. We identify the corresponding surface states by comparing the material’s bulk and surface spectra, finding two Fermi arcs that connect the projections of the Weyl nodes.
Our results expand the so-far only reluctantly-growing list of Weyl semimetal candidates, which are crucial for applications in next-generation devices.

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Presenters

  • Niclas Heinsdorf

    Goethe-Universität Frankfurt, ITP, Goethe University Frankfurt

Authors

  • Niclas Heinsdorf

    Goethe-Universität Frankfurt, ITP, Goethe University Frankfurt

  • Morten Holm Christensen

    School of Physics and Astronomy, University of Minnesota, University of Minnesota

  • Mikel Iraola

    Department of Condensed Matter Physics, University of the Basque Country UPV/EHU, Donostia International Physics Center, 20018 Donostia-San Sebastian, Spain

  • Shang-Shun Zhang

    University of Tennessee, School of Physics and Astronomy, University of Minnesota, Department of Physics and Astronomy, University of Tennessee, Knoxville, University of Minnesota

  • Turan Birol

    University of Minnesota, Department of Chemical Engineering and Materials Science, University of Minnesota, Physics, University of Minnesota, School of Physics and Astronomy, University of Minnesota

  • Cristian Batista

    University of Tennessee, Department of Physics & Astronomy, University of Tennessee, Knoxville, TN 37996, USA, Department of Physics and Astronomy, University of Tennessee, Physics and Astronomy, University of Tennessee, Oakridge National Laboratory, Department of Physics and astronomy, University of Tennessee, University of Tennessee, Knoxville, Department of Physics and Astronomy, University of Tennessee, Knoxville

  • Rafael Fernandes

    University of Minnesota, School of Physics and Astronomy, University of Minnesota, Physics, University of Minnesota, School of Physics and Astronomy, University of Minnesota, Minneapolis, 55455 MN, School of Physics and Astronomy, University of Minnesota, Minneapolis

  • Roser Valenti

    Goethe University Frankfurt, Goethe-Universität Frankfurt, Goethe University Frankfurt am Main, ITP, Goethe University Frankfurt, Institute for Theoretical Physics, Goethe-Universitat Frankfurt, Goethe-University Frankfurt, Institut für Theoretische Physik, Goethe University Frankfurt