Valency, charge-transfer, and orbital-dependent correlation in bilayer nickelates Nd3Ni2O7

TL;DR

This study investigates the complex electronic structure of Nd3Ni2O7 using advanced spectroscopy and theoretical methods, revealing unusual valence states and orbital-dependent interactions that deepen understanding of nickelate materials.

Contribution

It combines experimental spectroscopy with DFT+DMFT to uncover valence deviations and orbital effects in Nd3Ni2O7, a novel insight into nickelate electronic properties.

Findings

Ni 3d occupation deviates from formal valency, indicating charge transfer from oxygen.

Dominant d8 configuration with significant d7 and d9 contributions, showing unusual valence.

Orbital-dependent hybridization and correlation effects influence local spin dynamics.

Abstract

We examine the bulk electronic structure of Nd3Ni2O7 using Ni 2p core-level hard x-ray photoemission spectroscopy combined with density functional theory + dynamical mean-field theory. Our results reveal a large deviation of the Ni 3d occupation from the formal Ni2.5+ valency, highlighting the importance of the charge-transfer from oxygen ligands. We find that the dominant d8 configuration is accompanied by nearly equal contributions from d7 and d9 states, exhibiting an unusual valence state among Ni-based oxides. Finally, we discuss the Ni dx2-y2 and dz2 orbital-dependent hybridization, correlation and local spin dynamics.