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

Abstract Recent discovery of high transition temperature superconductivity in La 3 Ni 2 O 7 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 La 3 Ni 2 O 7 , where superconductivity emerges from the bilayer NiO 2 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.