Pairing symmetry and superconductivity in La₃Ni₂O₇ thin films

The recent discovery of superconductivity with a transition temperature Tc over 40 K in La₃Ni₂O₇ and (La,Pr)₃Ni₂O₇ thin films at ambient pressure marks an important step in the field of nickelate superconductors. Here, we perform a renormalized mean-field theory study of the superconductivity in La₃Ni₂O₇ thin films, using a bilayer two-orbital t - J model. Our result reveals an s±-wave pairing symmetry driven by the strong interlayer superexchange coupling of d_z2 orbital, resembling the pressurized bulk case. Also, we roughly reproduce the experimentally observed nodeless shape of the superconducting gap at the β pocket and the superconducting T_c. In addition, by analysing the orbital-resolved pairing configurations and their projections onto Fermi surface, we find that the nodeless feature of β pocket is related to the interlayer pairing within both d_z2 and d_x²-y² orbitals. Moreover, we identify a formation of the inplane inter-orbital d-wave pairing between d_z2 and d_x²-y² orbitals, which can even enhance the dominated interlayer s±-wave. Our study particularly highlights the diverse relations of different pairing channels in La₃Ni₂O₇ that holds a complex Fermi surface.