Electronic structure of SmOFeAs

The electronic structure of SmOFeAs, a parent compound of iron arsenic superconductors, is measured by angle resolved photoemission spectroscopy. Due to the surface contribution, the measured electronic structure deviates strongly from the calculations. One of the bulk bands is identified by photon energy dependence measurements. Moreover, the appearance of sharp quasiparticle peaks at low temperatures implies the drastic reduction of the scattering rate. No energy gap is observed at Fermi level, indicating that the Fermi surface nesting is irrelevant in the spin density wave formation.