Fermi surface and topology of the multiband superconductor BeAu

Abstract

The chiral material BeAu was recently identified as a multiband type-I superconductor with a critical temperature of 3.2 K. As a member of the B20 crystal family (space group P213), its band structure hosts multifold fermions at high-symmetry points, unpaired WPs, and even nodal surfaces. This renders BeAu an appealing system for investigating the interplay between superconductivity and topology. Here, we present a comprehensive first-principles analysis of BeAu's electronic structure, focusing on its Fermi surface's topology and the implications for superconductivity. Together with the presence of four- and sixfold fermions at high-symmetry points, we identify several additional isolated WPs near the Fermi level. We also determine the associated topological edge states—the surface Fermi arcs. Computing the Chern number associated to different Fermi surface sheets, we show that BeAu harbors a ν=4 topological superconducting phase in the presence of s-wave pairing of alternating sign (s± pairing). Notably, we also identify a Fermi surface with a Chern number of +6; the highest value reported to date. Finally, our analysis reveals strong inhomogeneity in the orbital character of electronic states at the Fermi level, suggesting a link to the observed multigap superconductivity.

Source-reported materials — not catalogue approval

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