Evidence from angle-resolved resonant photoemission for oxygen-2p nature of the Fermi-liquid states in Bi2CaSr2Cu2O8

Experimental results using the technique of angle-resolved resonant photoemission are presented which provide a clear picture of the electronic structure of the high-Tc superconductor Bi2CaSr2Cu2O8. The structure consists of two major features: a Fermi-liquid state with predominantly O 2p character and strongly localized states away from the Fermi level with both Cu 3d and O 2p character. Superconductivity could be driven by Cooper-pairing of the O 2p holes in the Fermi-liquid state.