Comparison in the electronic structure of YBa2Fe3O8 insulator with YBa2Cu3O7 and SmFeAsO0.8F0.2 superconductors

The electronic structure and chemical states of relevant elements of YBa2Fe3O8 are investigated using X-ray photoemission spectroscopy (XPS), compared with those of YBa2Cu3O7 and SmFeAsO0.8F0.2 superconductors. The typical differences and similarities in core-level and valence-band structures of these systems have been detected, strongly suggesting that the superconductivity have the finite density of states around Fermi level. Several features...