The recent discovery of a superconductivity signature in La3Ni2O7-{\delta} under a pressure of 14 GPa, with a superconducting transition temperature of around 80 K, has attracted considerable attention. An important aspect of investigating electronic structures is discerning the extent to which the electronic ground state of La3Ni2O7-{\delta} resembles the parent state of the cuprate superconductor, a charge transfer insulator with long-range antiferromagnetism. Through X-ray absorption spectroscopy, we have uncovered the crucial influence of oxygen ligands on the electronic ground states of the Ni ions, displaying a charge transfer nature akin to cuprate but with distinct orbital configurations. Both in-plane and out-of-plane Zhang-Rice singlets associated with Ni d_(x^2-y^2 ) and d_(z^2) orbitals are identified, together with a strong interlayer coupling through inner apical oxygen. Additionally, in La3Ni2O7-{\delta} films, we have detected a superlattice reflection (1/4, 1/4, L) at the Ni L absorption edge using resonant X-ray scattering measurements. Further examination of the resonance profile indicates that the reflection originates from the Ni d orbitals. By evaluating the reflection's azimuthal angle dependence, we have confirmed the presence of collinear antiferromagnetic spin ordering and charge-like anisotropy ordered with the same periodicity. Notably, our findings reveal a microscopic relationship between these two components in the temperature dependence of the scattering intensity of the reflection. This investigation enriches our understanding of high-temperature superconductivity in La3Ni2O7-{\delta} under high pressure.
@article{arxiv.2409.04121,
title = {Resolving the Electronic Ground State of La3Ni2O7-{\delta} Films},
author = {Xiaolin Ren and Ronny Sutarto and Xianxin Wu and Jianfeng Zhang and Hai Huang and Tao Xiang and Jiangping Hu and Riccardo Comin and X. J. Zhou and Zhihai Zhu},
journal= {arXiv preprint arXiv:2409.04121},
year = {2025}
}