2025/02/19 by Pietro Borchia, Borchia, Pietro, Hannah Lange +3 · 1 citation
Physics and Astronomy · #Physics of Superconductivity and Magnetism #Quantum, superfluid, helium dynamics #Rare-earth and actinide compounds
paper · pdf · doi:10.48550/arxiv.2502.13960
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 (MixD) 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 (DMRG) 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.