Nature Communications (May 2024)

Weyl spin-momentum locking in a chiral topological semimetal

  • Jonas A. Krieger,
  • Samuel Stolz,
  • Iñigo Robredo,
  • Kaustuv Manna,
  • Emily C. McFarlane,
  • Mihir Date,
  • Banabir Pal,
  • Jiabao Yang,
  • Eduardo B. Guedes,
  • J. Hugo Dil,
  • Craig M. Polley,
  • Mats Leandersson,
  • Chandra Shekhar,
  • Horst Borrmann,
  • Qun Yang,
  • Mao Lin,
  • Vladimir N. Strocov,
  • Marco Caputo,
  • Matthew D. Watson,
  • Timur K. Kim,
  • Cephise Cacho,
  • Federico Mazzola,
  • Jun Fujii,
  • Ivana Vobornik,
  • Stuart S. P. Parkin,
  • Barry Bradlyn,
  • Claudia Felser,
  • Maia G. Vergniory,
  • Niels B. M. Schröter

DOI
https://doi.org/10.1038/s41467-024-47976-0
Journal volume & issue
Vol. 15, no. 1
pp. 1 – 9

Abstract

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Abstract Spin-orbit coupling in noncentrosymmetric crystals leads to spin-momentum locking – a directional relationship between an electron’s spin angular momentum and its linear momentum. Isotropic orthogonal Rashba spin-momentum locking has been studied for decades, while its counterpart, isotropic parallel Weyl spin-momentum locking has remained elusive in experiments. Theory predicts that Weyl spin-momentum locking can only be realized in structurally chiral cubic crystals in the vicinity of Kramers-Weyl or multifold fermions. Here, we use spin- and angle-resolved photoemission spectroscopy to evidence Weyl spin-momentum locking of multifold fermions in the chiral topological semimetal PtGa. We find that the electron spin of the Fermi arc surface states is orthogonal to their Fermi surface contour for momenta close to the projection of the bulk multifold fermion at the Γ point, which is consistent with Weyl spin-momentum locking of the latter. The direct measurement of the bulk spin texture of the multifold fermion at the R point also displays Weyl spin-momentum locking. The discovery of Weyl spin-momentum locking may lead to energy-efficient memory devices and Josephson diodes based on chiral topological semimetals.