Parameter-Dependent Superconducting Transition Temperature in a Sign-Problem-Free Bilayer Model

Abstract Recent discovery of high transition temperature superconductivity in La₃Ni₂O₇ has sparked renewed theoretical and experimental interests in unconventional superconductivity. It is crucial to understand the influence of various factors on its superconductivity. By refining the determinant quantum Monte Carlo algorithm, we characterize the parameter dependence of the superconducting transition temperature within a bilayer Hubbard model, which is sign-problem-free at arbitrary filling. A striking feature of this model is its similarity to the bilayer nickelate-based superconductor La₃Ni₂O₇, where superconductivity emerges from the bilayer NiO₂ planes. We find that interlayer spin-exchange J is critical to interlayer pairing, and that on-site interaction U contributes negatively to superconductivity at low doping levels but positively at high doping levels. Our findings can provide a reference for the next step in theoretical research on nickelate-based superconductors.