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arXiv · 2107.02820

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

Nico Huber·Kirill Alpin·Grace L. Causer·Lukas Worch·Andreas Bauer·Georg Benka·Moritz M. Hirschmann·Andreas P. Schnyder·Christian Pfleiderer·Marc A. Wilde
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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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Nico Huber, Kirill Alpin, Grace L. Causer, Lukas Worch, Andreas Bauer, Georg Benka, Moritz M. Hirschmann, Andreas P. Schnyder, Christian Pfleiderer, Marc A. Wilde. 2021-07-06. Network of topological nodal planes, multifold degeneracies, and Weyl points in CoSi. https://doi.org/10.1103/physrevlett.129.026401

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