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The pairing symmetry of the recently discovered bilayer nickelate superconductor La₃Ni₂O₇ is a subject of intense debate in condensed matter physics, with the two leading theoretical candidates being a sign-reversing s_-wave and a d-wave state. To investigate its ground-state properties in the intermediate coupling regime which is critical for real materials, we construct a two-orbital bilayer Hubbard model and employ the constrained-path quantum Monte Carlo method for large-scale simulations. By systematically calculating ground-state pairing correlation functions across parameter spaces, we map its pairing symmetry phase diagram. We find that an increasing Hund's coupling selectively enhances the interlayer s_-wave pairing while suppressing the intralayer d-wave pairing. Similarly, a larger crystal field splitting drives a transition from d-wave- to s_-wave-dominant states. Further analysis reveals that the strength of the intralayer d-wave pairing is strongly correlated with the (π, π) antiferromagnetic spin fluctuations, which are in turn effectively suppressed by a large crystal field splitting, thereby weakening the d-wave pairing channel. Additionally, the dominant pairing symmetry transition region roughly overlaps with the inversion of orbital occupancy response to Hubbard U, suggesting an intrinsic link between pairing competition and orbital physics. Our results indicate that, within the parameter regime relevant to the actual material, the s_-wave is the most probable pairing symmetry.
Xiong et al. (Wed,) studied this question.