Surface-driven electronic structure in LaFeAsO studied by angle-resolved photoemission spectroscopy

We measured the electronic structure of an iron arsenic parent compound LaFeAsO using angle-resolved photoemission spectroscopy (ARPES). By comparing with a full-potential linear augmented plane wave calculation we show that the extra large $\ensuremath{\Gamma}$ hole pocket measured via ARPES comes from electronic structure at the sample surface. Based on this we discuss the strong-polarization dependence of the band structure and a temperature-dependent holelike band around the $M$ point. The two phenomena give additional evidences for the existence of the surface-driven electronic structure.