Orbital symmetry of Ba(Fe1-xCox)2As2 superconductors probed with x-ray absorption spectroscopy

The orbital symmetries of electron-doped iron-arsenide superconductors Ba(Fe1-xCox)(2)As-2 have been measured with x-ray absorption spectroscopy. The data reveal signatures of Fe d electron itinerancy, weak electronic correlations, and a high degree of Fe-As hybridization related to the bonding topology of the Fe d(xz+yz) states, which are found to contribute substantially at the Fermi level. The energies and detailed orbital character of Fe and As derived unoccupied s and d states are found to be in remarkably good agreement with the predictions of standard density-functional theory.