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 La_2.85Pr_0.15Ni₂O₇film grown on SrLaAlO₄by fluctuation-exchange approximation. The<i>γ</i>and<i>δ</i>bands are found to shift down with correlation while their Fermi surfaces become highly damped and cannot to be resolved experimentally. In contrast, the<i>α</i>and<i>β</i>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<i>γ</i>band and the asymmetric<i>δ</i>band. The superconducting pairing symmetry is robustly<i>s</i>-wave and the<i>δ</i>band has the largest pairing magnitude. All the findings suggest a dominant role of the3dz2orbital in this material.