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Extended s-wave pairing from an emergent Feshbach resonance in bilayer nickelate superconductors

Pietro Borchia1,2,*, Hannah Lange1,3,4, and Fabian Grusdt1,4

  • *Contact author: pietro.borchia@univie.ac.at
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Phys. Rev. B 112, 165143 – Published 27 October, 2025

DOI: https://doi.org/10.1103/q8qm-1ttf

Abstract

Since the discovery of unconventional superconductivity in cuprates, unraveling the pairing mechanism of charge carriers in doped antiferromagnets has been a long-standing challenge. Motivated by the discovery of high-Tc superconductivity in nickelate bilayer La3Ni2O7 (LNO), we study a minimal mixed dimensional t−J model supplemented with a repulsive Coulomb interaction V. When hole doped, previous numerical simulations revealed that the system exhibits strong binding energies, with a phenomenology resembling a BCS-to-BEC crossover accompanied by a Feshbach resonance between two distinct types of charge carriers. Here, we perform a mean-field analysis that enables a direct observation of the BCS-to-BEC crossover as well as microscopic insights into the crossover region and the pairing symmetry for two-dimensional bilayers. We benchmark our mean-field description by comparing it to density-matrix renormalization group simulations in quasi-one-dimensional settings and find remarkably good agreement. For the two-dimensional system relevant to LNO, our mean-field calculations predict a BCS pairing gap with an extended s-wave symmetry, directly resulting from the pairing mechanism's Feshbach origin. Our analysis hence gives insights into pairing in unconventional superconductors and, further, can be tested in currently available ultracold atom experiments.

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Phys. Rev. B 112, 165143– Published 27 October, 2025
  • Received 10 March 2025
  • Accepted 10 October 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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