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TT: Fachverband Tiefe Temperaturen

TT 6: Topological Semimetals

TT 6.13: Talk

Monday, March 27, 2023, 12:45–13:00, HSZ 304

Weyl-type parallel spin-momentum locking in a chiral topological semimetal — •Niels B. M. Schröter — Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany

Orthogonal Rashba-type spin-momentum locking is well-known from semiconductors and topological insulator surface states and has inspired many theoretical proposals for technological applications. In contrast, Weyl-type purely parallel spin-momentum locking – which can be considered the natural counterpart of the Rashba-type – has remained elusive in experiments because all experimentally confirmed Weyl-fermion are described by Pauli matrices that act on an orbital pseudospin rather than the proper electron spin. Recently, chiral topological semimetals (CTS) that host single- and multifold band crossings [1,2] have been predicted to realize parallel spin-momentum locking. Here, we use spin-resolved photoemission to probe the spin-texture Fermi-arc surface states in the CTS PtGa. We find that the electron spin points orthogonal to the Fermi surface contour for momenta close to the projection of a bulk multifold fermion, which is consistent with parallel spin-momentum locking of the latter [3]. We anticipate that our discovery of parallel spin-momentum locking of multifold fermions will lead to the integration of chiral topological semimetals in novel spintronic devices that can be used for field-free switching of magnets with perpendicular magnetic anisotropy, and other novel phenomena.

[1] Schröter et al., Nat. Phys 8 759-65 (2019)

[2] Schröter et al., Science 369, 179-83 (2020)

[3] Krieger et al., arXiv.2210.08221 (2022)