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Optical signatures of multifold fermions in the chiral topological semimetals RhSi and CoSi

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Abstract

The chiral topological semimetals RhSi and CoSi exhibit band degeneracies near the Fermi level enforced by the crystal symmetries. The low-energy quasiparticles emerging near these band degeneracies, referred to as multifold fermions, have no counterpart as elementary fermionic particles. We calculate the linear optical conductivity of all chiral multifold fermions[1] and show that it provides an experimental fingerprint for each type of multifold fermion. We use a tight-binding model for space group 198, where RhSi and CoSi crystallize, and obtain the parameters for both materials from first-principles calculations. The results reveal that the location of the chemical potential is crucial to understand the optical response seen in experiments[2,3], determined at low energies by the threefold fermion at the Γ point in both materials, and providing signatures of the existence of a spin-3/2 fourfold fermion in CoSi.

[1] M.-Á S.-M. et al., Phys. Rev. B, 99 155145 (2019).
[2] B. Xu et al, PNAS Nov 2020, 117 (44) 27104-27110
[3] Z. Ni et al., arXiv:2005.13473 (2020).

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Presenters

  • Miguel Ángel Sánchez Martínez

    Institut Neel, CNRS and Universite Grenoble Alpes

Authors

  • Miguel Ángel Sánchez Martínez

    Institut Neel, CNRS and Universite Grenoble Alpes

  • Bing XU

    University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials,, University of Fribourg

  • Zhenyao Fang

    Department of Chemistry, University of Pennsylvania

  • Zhuoliang Ni

    University of Pennsylvania, Department of Physics and Astronomy, University of Pennsylvania

  • Jorn W. F. Venderbos

    Department of Physics, Drexel University, Philadelphia, PA 19104, USA, Drexel University, Department of Physics, Department of Materials Science and Engineering, Drexel University

  • Fernando De Juan

    Donostia International Physics Center, Donostia International Physics Center and IKERBASQUE, Basque Foundation for Science

  • Eugene John Mele

    Department of Physics and Astronomy, University of Pennsylvania, University of Pennsylvania

  • Andrew Marshall Rappe

    Chemistry, University of Pennsylvania, University of Pennsylvania, Department of Chemistry, University of Pennsylvania

  • Adolfo G Grushin

    Institut Néel, CNRS and Université Grenoble Alpes, Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Institut Neel, CNRS Institut Néel, Institut Neel, CNRS and Universite Grenoble Alpes

  • Liang Wu

    University of Pennsylvania, Department of Physics and Astronomy, University of Pennsylvania