and Isoelectronic Cuprate Superconductors*

It is an open question whether layered nickelate compounds and derived heterostructures could mimic a set of distinct properties which are suspected to invoke high-temperature superconductivity in cuprates, that is, a 2D layered crystal structure, spin 1/2 and strong antiferromagnetic correlations in the parent compound, absence of orbital degeneracy, and hybridization with oxygen ligands. To address this issue, we have investigated LaNiO₂ and isostructural SrCuO₂ thin films by x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) at the O K -and Ni L-edges. Despite several formal similarities between the nickelate and the cuprate, our study unveils severe differences in orbital configuration, antiferromagnetic order, and ligand-hybridization.