Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors. arXiv submission processing window: times are unavailable (UTC).

1. From perovskite to infinite-layer nickelates: hole concentration from x-ray absorption

Summary: This study systematically investigated the evolution of PrNiOₓ thin films at various intermediate stages of topological reduction (x = 2–3) using soft X-ray absorption spectroscopy. By comparing Ni L-edge experimental spectra with single-cluster and double-cluster ligand-field model calculations, it was found that none of the samples exhibited a pure d⁹ electronic configuration. Quantitative analysis based on the charge sum rule revealed that even in the most reduced films, the average number of Ni 3d holes remained 1.35, while superconducting samples displayed higher hole counts, challenging previous assumptions regarding the hole doping limit. Concurrent changes in the O K-edge absorption spectra during reduction indicated the presence of O 2p holes even in the most reduced films. Collectively, these results suggest that a complex hole doping mechanism arises from the interplay between self-doping effects and oxygen non-stoichiometry.