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. Observation of correlated plasmons in low-valence nickelates

Summary: Using resonant inelastic X-ray scattering (RIXS) at the oxygen K-edge, plasmon collective excitations were observed in the low-valence nickelate Pr4Ni3O8 and compared with the overdoped cuprate La₂₋ₓSrₓCuO₄. The experiments revealed that the nickelate plasmons exhibit dispersive behavior within the in-plane momentum, but with significantly lower velocity and stronger damping than the cuprate, and they become overdamped and disappear at much smaller momenta. Random phase approximation (RPA) calculations indicate that these differences originate from reduced electron hopping and enhanced long-range Coulomb interaction screening in the nickelate, where both the in-plane hopping integral and Coulomb interaction strength are substantially smaller than in the cuprate. Furthermore, the out-of-plane plasmons in the nickelate showed no discernible dispersion, possibly due to its trilayer coupling structure. Temperature-dependent studies found that the plasmons in Pr4Ni3O8 soften with increasing temperature, whereas in the cuprate the energy remains nearly constant while damping increases, suggesting the presence of additional correlations such as stripe fluctuations in the nickelate. These results reveal a unique charge screening landscape in nickelates, where weakened electron hopping and enhanced Coulomb screening are key distinguishing features from cuprates, potentially explaining the lower superconducting transition temperature of nickelates and providing quantitative experimental constraints for analogies between the two material families.