Theoretical study of the electronic correlation and superconducting pairing in La$_{2.85}$Pr$_{0.15}$Ni$_2$O$_7$ film grown on SrLaAlO$_4$

TL;DR

This study uses fluctuation-exchange approximation to analyze electronic correlations and superconducting pairing in La$_{2.85}$Pr$_{0.15}$Ni$_2$O$_7$ films, highlighting the importance of the $3d_{z^{2}}$ orbital and identifying an $s$-wave pairing symmetry.

Contribution

It provides a theoretical analysis of electronic correlations and superconducting pairing mechanisms in La$_{2.85}$Pr$_{0.15}$Ni$_2$O$_7$ using fluctuation-exchange approximation, emphasizing the role of specific orbitals.

Findings

The $eta$ and $eta$ Fermi surfaces remain sharp and detectable.

Spin susceptibility peaks at a wave vector connecting $eta$ and $eta$ bands.

Superconducting pairing symmetry is robustly $s$-wave with the $eta$ band having the largest pairing magnitude.

Abstract

We investigate the electronic correlation effects in La$_{2.85}$Pr$_{0.15}$Ni$_2$O$_7$ film grown on SrLaAlO$_4$ by fluctuation-exchange approximation. The $\gamma$ and $\delta$ bands are found to shift down with correlation while their Fermi surfaces become highly damped and cannot to be resolved experimentally. In contrast, the $\alpha$ and $\beta$ 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 $\gamma$ band and the asymmetric $\delta$ band. The superconducting pairing symmetry is robustly $s$-wave and the $\delta$ band has the largest pairing magnitude. All the findings suggest a dominant role of the $3d_{z^{2}}$ orbital in this material.