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  • Open Access

Optical signatures of Euler superconductors

Chun Wang Chau1,*, Wojciech J. Jankowski1, and Robert-Jan Slager1,2,†

  • *Contact author: cwc61@cam.ac.uk
  • †Contact author: rjs269@cam.ac.uk
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Phys. Rev. B 112, 064512 – Published 11 August, 2025

DOI: https://doi.org/10.1103/b9ll-927t

Abstract

We study optical manifestations of multigap band topology in multiband superconductors with a nontrivial topological Euler class. We introduce a set of lattice models for non-Abelian superconductors with the Euler invariant signified by a nontrivial quantum geometry. We then demonstrate that the topological Bogoliubov excitations realized in these models provide for a characteristic first-order optical response distinct from those of the other known topological superconductors. We find that the spectral distribution of the optical conductivity universally admits a topological jump originating from the Euler class in the presence of d-wave superconducting pairings and naturally differs from the features induced by the quantum geometry in the noninteracting bands without pairing terms. Further to uncovering observable signatures in first-order optical conductivities, we showcase that the higher-order optical responses of the non-Abelian Euler superconductor can result in enhanced nonlinear currents that fingerprint the exotic topological invariant. Finally, by employing a diagrammatic approach, we generalize our findings beyond the specific models of Euler superconductors.

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Phys. Rev. B 112, 064512– Published 11 August, 2025
  • Received 6 January 2025
  • Revised 14 July 2025
  • Accepted 16 July 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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