Krieger Jonas A, Stolz Samuel, Robredo Iñigo, Manna Kaustuv, McFarlane Emily C, Date Mihir, Pal Banabir, Yang Jiabao, B Guedes Eduardo, Dil J Hugo, Polley Craig M, Leandersson Mats, Shekhar Chandra, Borrmann Horst, Yang Qun, Lin Mao, Strocov Vladimir N, Caputo Marco, Watson Matthew D, Kim Timur K, Cacho Cephise, Mazzola Federico, Fujii Jun, Vobornik Ivana, Parkin Stuart S P, Bradlyn Barry, Felser Claudia, Vergniory Maia G, Schröter Niels B M
Max Planck Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle, Germany.
Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen PSI, Switzerland.
Nat Commun. 2024 May 2;15(1):3720. doi: 10.1038/s41467-024-47976-0.
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.
非中心对称晶体中的自旋-轨道耦合导致自旋-动量锁定——电子的自旋角动量与其线性动量之间的一种定向关系。各向同性正交 Rashba 自旋-动量锁定已被研究了数十年，而其对应物，各向同性平行 Weyl 自旋-动量锁定在实验中仍然难以实现。理论预测，Weyl 自旋-动量锁定只能在结构手性立方晶体中，在克莱默斯-外尔或多重费米子附近实现。在此，我们使用自旋和角分辨光电子能谱来证明手性拓扑半金属 PtGa 中多重费米子的 Weyl 自旋-动量锁定。我们发现，对于接近体多重费米子在 Γ 点投影的动量，费米弧表面态的电子自旋与其费米面轮廓正交，这与后者的 Weyl 自旋-动量锁定一致。在 R 点对多重费米子的体自旋纹理的直接测量也显示出 Weyl 自旋-动量锁定。Weyl 自旋-动量锁定的发现可能会带来基于手性拓扑半金属的节能存储器件和约瑟夫森二极管。
