Application of Generalized Periodic Anderson Hamiltonians to the Superconducting Nickelates

TL;DR

This paper uses a 3D dispersing Periodic Anderson Model and functional Renormalization Group methods to investigate the emergence of superconductivity in Nickelates, highlighting the roles of orbital hybridization and out-of-plane hopping.

Contribution

It introduces a 3D ab-initio PAM model for Nickelates and demonstrates how hybridization and hopping influence different superconducting orders.

Findings

Hybridization with interstitial-s band promotes 3D d_z^2-type superconductivity.

Out-of-plane hopping enhances s-wave superconductivity.

d_{x^2-y^2} superconductivity naturally arises in the models.

Abstract

We study the extent to which a three-dimensional dispersing Periodic Anderson Model (PAM) can explain the emergence of novel superconductivity in the Infinite-Layer Nickelate compounds. By going beyond frequently used 2D models, the 3D dispersing PAM allows us to incorporate effects of finite out-of-plane hopping and orbital hybridization in describing these systems. Using an unbiased functional Renormalization Group (fRG) approach, we show that $d_{x^2-y^2}$ superconductivity arises in a series of 3D {\it {ab-initio}} models of the Nickelates ({\it {e.g.}}$\mathrm{RNiO_2}$), where R is a rare earth element. We the study the impact of going beyond the Ni-d orbital by including the R-$d_{z^2}$ and the interstitial-$s$ as hybridizing conducting bands. We explore the dependence of the models on key parameters, including the local Hubbard coupling, doping and temperature. We find the hybridization with the interstitial-$s$ band driving a 3D $d_{z^2-r^2}$-type superconductivity while out of plane hopping primarily enhances an $s$-wave superconducting order.