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.

*I want to thank the Foundation of the Polytechnical Society (SPTG) in Frankfurt for funding me during my master's.

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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