Pairing Symmetry and Superconductivity in La 3 Ni 2 O 7 Thin Films

Abstract The recent discovery of superconductivity with a transition temperature T c over 40 K in La 3 Ni 2 O 7 and (La,Pr) 3 Ni 2 O 7 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 La 3 Ni 2 O 7 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 z 2 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 z 2 and d x 2 - y 2 orbitals. Moreover, we identify a formation of the inplane inter-orbital d-wave pairing between d z 2 and d x 2 - y 2 orbitals, which can even enhance the dominated interlayer s ± -wave. Our study particularly highlights the diverse relations of different pairing channels in La 3 Ni 2 O 7 that holds a complex Fermi surface.