Resonant inelastic x-ray scattering study of charge excitations in superconducting and nonsuperconducting PrFeAsO 1 − y

We report the first observation by momentum-resolved resonant inelastic x-ray scattering of charge excitations in an iron-based superconductor and its parent compound, PrFeAsO0.7 and PrFeAsO, respectively, with two main results. First, using calculations based on a 16-band dp model, we show that the energy of the lowest-lying excitations, identified as dd interband transitions of dominant xz, yz orbital character, exhibits a dramatic dependence on electron correlation. This enables us to estimate the Coulomb repulsion U and Hund's coupling J, and to highlight the role played by J in these peculiar orbital-dependent electron correlation effects. Second, we show that short-range antiferromagnetic correlations, which are a prerequisite to the occurrence of these excitations at the Gamma point, are still present in the superconducting state.