A central question in the study of infinite-layer nickelates is their relationship to cuprates. In particular, understanding how electron correlations differ between infinite-layer nickelates and cuprates is essential for identifying the microscopic ingredients that control their magnetic and electronic ground states.

To address this question, we performed resonant inelastic x-ray scattering (RIXS) measurements on infinite-layer PrNiO₂ and compared its collective excitations with those of the isostructural cuprate SrCuO₂. Our experiments reveal dispersive magnetic excitations in PrNiO₂ with a magnon bandwidth of approximately 180 meV, about half that observed in SrCuO₂, indicating a substantially reduced magnetic energy scale in the nickelate. By analyzing the magnon dispersion within a Hubbard-Heisenberg framework, we find that although the effective Coulomb interaction U is lower in PrNiO₂ than in SrCuO₂, the reduced hopping amplitude leads to a larger correlation ratio U/t in PrNiO₂.

These results demonstrate that PrNiO₂ is more strongly correlated than its infinite-layer cuprate counterpart, despite having a smaller absolute Coulomb interaction. Our work provides an experimental route to quantify correlation strength from spin excitations and offers new insights into the distinct magnetic and electronic properties of infinite-layer nickelates and cuprates.

This work has been published in Communications Materials (X. Hong, Y. Wu, Q. Wang^✉, J. Chang et al. Impact of electron correlations on infinite-layer cuprates and nickelates. https://doi.org/10.1038/s43246-026-01175-0). We are thankful to all collaborators.