SKM 2021 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 27: Topological Insulators and Semimetals (joint session TT/KFM)
TT 27.4: Talk
Friday, October 1, 2021, 10:45–11:00, H7
Network of topological nodal planes and point degeneracies in CoSi — •Nico Huber1, Kirill Alpin2, Grace L. Causer1, Lukas Worch1, Andreas Bauer1, Georg Benka1, Moritz M. Hirschmann2, Andreas P. Schnyder2, Christian Pfleiderer1, and Marc A. Wilde1 — 1Physik Department, Technische Universität München, D-85748 Garching, Germany — 2Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
We report the experimental identification of symmetry-enforced topological nodal planes in CoSi which together with multifold point degeneracies and Weyl points form a network of band crossings satisfying the fermion doubling theorem. For this, we have combined measurements of Shubnikov-de Haas oscillations in CoSi with material-specific electronic structure calculations and a symmetry analysis [1]. The observation of two nearly dispersionless Shubnikov-de Haas frequency branches is shown to provide clear evidence of four distinct Fermi surface sheets at the R point of the Brillouin zone and of the symmetry-enforced orthogonality of the wave functions at the intersections with the nodal planes. These results highlight that CoSi features six- and fourfold crossings at R and Γ and that a comprehensive account of all topological charges in the network going beyond point degeneracies is needed.
[1] Huber et al., arXiv:2107.02820