We investigated the recently found superconductor ${\text{LaFeAsO}}_{1-x}{\text{F}}_x$ by x-ray absorption spectroscopy. From a comparison of the $\text{O}K$ edge with LDA calculations we find good agreement and are able to explain the structure and changes in the spectra with electron doping. From experimental $\text{Fe}{L}_{2,3}$-edge spectra and charge-transfer multiplet calculations we gain further information on important physical values such as the hopping parameters, the charge-transfer energy $\Delta$, and the Hubbard $U$. Furthermore we find the system to be very covalent with a large amount of ligand holes. A shift in the chemical potential is visible in the $\text{O}K$- and $\text{Fe}{L}_{2,3}$-edge spectra which emphasizes the importance of band effects in these compounds. From the entirety of our results we conclude that LaFeAsO is a bandwidth-dominated material.

• Received 20 June 2008

DOI:https://doi.org/10.1103/PhysRevB.78.220502