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By simultaneously measuring the resistance and diamagnetism of (La,Pr)3Ni2O7 thin films and mapping the vortex-melting phase diagram under in-plane and out-of-plane magnetic fields, we investigated the anisotropy of superconductivity in bilayer nickelates. For H ∥ c, geometric confinement in ultrathin films leads to pancake vortices; the vortex-melting-field anisotropy parameter γ_Hm = H_m^ab/H_m^c decreases monotonically with decreasing temperature and approaches 1 at low temperatures, indicating the formation of a nearly isotropic vortex solid. Within anisotropic Ginzburg-Landau scaling, this ratio reflects the anisotropy of the superfluid density, and the results therefore point to a nearly isotropic superfluid response; this is incompatible with a contribution solely from the strictly two-dimensional Ni 3d_{x^2-y^2} band, but is naturally explained by a significant interlayer superfluid weight provided by the Ni 3d_{z^2}-derived γ band. This work provides thermodynamic evidence that superconductivity in bilayer nickelate thin films includes a substantial contribution from the γ band.

By combining density functional theory, dynamical mean-field theory, and the random phase approximation to solve the superconducting gap equation, researchers have discovered that hole-doped layered nickel oxide La₃₋ₓSrₓNi₂O₇ can achieve bulk superconductivity under ambient pressure. When the doping concentration x approaches 0.4, the γ Fermi pocket derived from the Ni-d₃z²₋r² orbital evolves from a circular to a diamond shape and expands to half the Brillouin zone, forming a nearly perfect Fermi surface nesting with an optimal nesting vector Q=(π, π). This structure significantly enhances antiferromagnetic spin fluctuations, elevating the superconducting eigenvalue to experimentally observable levels without the need for high pressure or strain. This work elucidates the mechanism by which hole doping modulates the shape and size of the Fermi pocket, providing a theoretical foundation and an experimentally feasible pathway for realizing the long-sought bulk superconductivity in such materials under ambient conditions.