The electronic structure of Bi2(Sr,Ca)3Cu2Oy has been studied by photoemission and electron-energy-loss spectroscopy (EELS). From analysis of the Cu 2p core-level photoemission spectra, the Cu 3d-O 2p bond in the CuO2 layer is found to be more ionic than that in La2-xSrxCuO4 and YBa2Cu3Oy, which leads to a weaker superexchange coupling between the Cu2+ spins within the layer. Valence-band photoemission and EELS spectra suggest a significant shift of the Bi 6s contribution from the deep-lying Bi 6s-O 2p bonding states to the antibonding states in the O 2p band region as compared to the results of band-structure calculations on Bi2Sr2CaCu2O8. This is probably due to excess oxygen atoms around Bi, which may raise the Bi 6s orbital energy and provide the system with holes.
ASJC Scopus subject areas
- Condensed Matter Physics