Electronic Structure and Electron Correlation in LaFeAsO_{1-x}F_x and   LaFePO_{1-x}F_x
  Photoemission spectroscopy is used to investigate the electronic structure of the newly discovered iron-based superconductors LaFeAsO_{1-x}F_x and LaFePO_{1-x}F_x. Line shapes of the Fe 2p core-level spectra suggest an itinerant character of Fe 3d electrons. The valence-band spectra are generally consistent with band-structure calculations except for the shifts of Fe 3d-derived peaks toward the Fermi level. From spectra taken in the Fe 3p -> 3d core-absorption region, we have obtained the experimental Fe 3d partial density of states, and explained it in terms of a band-structure calculation with a phenomenological self-energy correction, yielding a mass renormalization factor of ~< 2. 
Walid Malaeb, Teppei Yoshida, Takashi Kataoka, Atsushi Fujimori,   Masato Kubota, Kanta Ono, Hidetomo Usui, Kazuhiko Kuroki,...