Theoretical study of the electronic correlation and superconducting pairing in La 2.85 Pr 0.15 Ni 2 O 7 film grown on SrLaAlO 4.

We investigate the electronic correlation effects in La2.85Pr0.15Ni2O7 film grown on SrLaAlO4 by fluctuation-exchange approximation. The γ and δ bands are found to shift down with correlation while their Fermi surfaces become highly damped and cannot to be resolved experimentally. In contrast, the α and β Fermi surfaces do not vary much with correlation and they are sharp enough to be detected in experiments. The spin susceptibility peaks at a wave vector in the odd channel, connecting the symmetric γ band and the asymmetric δ band. The superconducting pairing symmetry is robustly s-wave and the δ band has the largest pairing magnitude. All the findings suggest a dominant role of the 3d z 2 orbital in this material.