Character of Doped Holes in Nd$_{1-x}$Sr$_x$NiO$_2$

TL;DR

This study explores how charge distribution and interactions in layered nickelate superconductors evolve with doping and charge-transfer energy, revealing the roles of Coulomb interactions and rare-earth atoms in their electronic properties.

Contribution

It introduces an analysis of charge transfer, Coulomb interactions, and orbital effects in nickelates, highlighting the crossover from cuprate-like to local triplet regimes and the significance of rare-earth atoms.

Findings

Charge-transfer energy influences the crossover from cuprate to triplet regimes.

Coulomb interaction U_{dp} reduces Zhang-Rice singlet stability.

Antiferromagnetic interactions dominate in electron-doped regimes.

Abstract

We investigate charge distribution in the recently discovered high-$T_c$ superconductors, layered nickelates. With increasing value of charge-transfer energy we observe the expected crossover from the cuprate to the local triplet regime upon hole doping. We find that the $d-p$ Coulomb interaction $U_{dp}$ plays a role and makes Zhang-Rice singlets less favorable, while the amplitude of local triplets is enhanced. By investigating the effective two-band model with orbitals of $x^2-y^2$ and $s$ symmetries we show that antiferromagnetic interactions dominate for electron doping. The screened interactions for the $s$ band suggest the importance of rare-earth atoms in superconducting nickelates.