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  • Letter
  • Open Access

Singlet, triplet, and mixed all-to-all pairing states emerging from incoherent fermions

Jagannath Sutradhar1,2,*, Jonathan Ruhman2, and Avraham Klein1

  • *Contact author: sutradj@biu.ac.il
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Phys. Rev. Research 6, L042036 – Published 4 November, 2024

DOI: https://doi.org/10.1103/PhysRevResearch.6.L042036

Abstract

The electron-electron and electron-phonon coupling in complex materials can be more complicated than simple density-density interactions, involving intertwined dynamics of spin, charge, and spatial symmetries. This motivates studying universal models with complex interactions and whether BCS-type singlet pairing is still the “natural” fate of the system. To this end, we construct a Yukawa-SYK model with nonlocal couplings in both spin and charge channels. Furthermore, we provide for time-reversal-symmetry breaking dynamics by averaging over the Gaussian unitary ensemble rather than the orthogonal ensemble. We find that the ground state of the system can be an orbitally nonlocal superconducting state arising from incoherent fermions with no BCS-like analog. The superconductivity has an equal tendency to triplet and singlet pairing states separated by a non-Fermi liquid phase. We further study the fate of the system within the superconducting phase and find that the expected ground state, away from the critical point, is a mixed singlet/triplet state. Finally, we find that, while at Tc the triplet and singlet transitions are dual to one another, below Tc the duality is broken, with the triplet state more susceptible to orbital fluctuations just by its symmetry. Our results indicate that such fluctuation-induced mixed states may be an inherent feature of strongly correlated materials.

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Phys. Rev. Research 6, L042036– Published 4 November, 2024
  • Received 15 April 2024
  • Accepted 23 September 2024
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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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