Resonant inelastic X-ray scattering in single-crystal superconducting PrFeAsO

Jarrige, I.; Ishii, Kenji; Ikeuchi, Kazuhiko*; Yoshida, Masahiro; Ishikado, Motoyuki; Hiraoka, Nozomu*; Tsuei, K.-D.*; Iyo, Akira*; Eisaki, Hiroshi*; Kito, Hijiri*; Shamoto, Shinichi  

A prerequisite to elucidate the mechanism underlying superconductivity in the iron oxypnictides is an in-depth knowledge of the low-lying electronic excitations. In an attempt to unveil those low-energy excitations, we have performed a resonant inelastic X-ray scattering (RIXS) measurement at the Fe K edge in a single crystal of the underdoped superconductor compound PrFeAsO (Tc = 42 K). We discern a feature centered around 4 eV which is reminiscent of the metal-ligand charge transfer in the cuprates, therefore we are tempted to ascribe it to the charge transfer between Fe 3d and As 4p.