title: Orbital symmetry and electron correlation in NaxCoO2.
abstract: Measurements of polarization-dependent soft x-ray absorption reveal that the electronic states determining the low-energy excitations of NaxCoO2 have predominantly a(1g) symmetry with significant O 2p character. In contrast to the prediction of band theory, doping-dependent O 1s x-ray absorption shows a large transfer of spectral weight, providing spectral evidence for strong electron correlations of the layered cobaltates. We also found that NaxCoO2 exhibits a charge-transfer electronic character rather than a Mott-Hubbard character.
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
authors.forename: W B
authors.initials: WB
authors.lastname: Wu
authors.forename: D J
authors.initials: DJ
authors.lastname: Huang
authors.forename: J
authors.initials: J
authors.lastname: Okamoto
authors.forename: A
authors.initials: A
authors.lastname: Tanaka
authors.forename: H-J
authors.initials: HJ
authors.lastname: Lin
authors.forename: F C
authors.initials: FC
authors.lastname: Chou
authors.forename: A
authors.initials: A
authors.lastname: Fujimori
authors.forename: C T
authors.initials: CT
authors.lastname: Chen