Network of topological nodal planes, multifold degeneracies, and Weyl points in CoSi

Abstract

We report the identification of symmetry-enforced nodal planes (NPs) in CoSi providing the missing topological charges in an entire network of band-crossings comprising in addition multifold degeneracies and Weyl points, such that the fermion doubling theorem is satisfied. In our study we have combined measurements of Shubnikov-de Haas (SdH) oscillations in CoSi with material-specific calculations of the electronic structure and Berry curvature, as well as a general analysis of the band topology of space group (SG) 198. The observation of two nearly dispersionless SdH frequency branches provides unambiguous evidence of four Fermi surface sheets at the R point that reflect the symmetry-enforced orthogonality of the underlying wave functions at the intersections with the NPs. Hence, irrespective of the spin-orbit coupling strength, SG198 features always six- and fourfold degenerate crossings at R and $\Gamma$ that are intimately connected to the topological charges distributed across the network.

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• Hierarchy of quasi-symmetries and degeneracies in chiral crystal materials CoSi
• Altermagnetic Instabilities from Quantum Geometry
• Fundamental laws of chiral band crossings: local constraints, global constraints, and topological phase diagrams
• Fermi surface of the chiral topological semimetal CoSi
• Electrical conductivity and screening effect of spin-1 chiral fermions scattered by charged impurities
• NiSi: New venue for antiferromagnetic spintronics
• Quantum Geometric Origin of the Intrinsic Nonlinear Hall Effect
• Band Curvature Effects on Quantum Transport of Spin-1 Chiral Fermion Systems
• Quantum geometry and low-frequency optical conductivity of nodal planes