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.
Cite
@article{arxiv.2502.11327,
title = {Valency, charge-transfer, and orbital-dependent correlation in bilayer nickelates Nd3Ni2O7},
author = {Daisuke Takegami and Takaki Okauchi and Edgar Abarca Morales and Kouto Fujinuma and Mizuki Furo and Masato Yoshimura and Ku-Ding Tsuei and Grace A. Pan and Dan Ferenc Segedin and Qi Song and Hanjong Paik and Charles M. Brooks and Julia A. Mundy and Takashi Mizokawa and Liu Hao Tjeng and Berit H. Goodge and Atsushi Hariki},
journal= {arXiv preprint arXiv:2502.11327},
year = {2025}
}