Browsing by Author "Chou, FC"

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Orbital symmetry and electron correlation in NaxCoO2
(2005-04-15)
Wu, WB
;
Huang, DJ
;
Okamoto, J
;
Tanaka, A
;
Lin, HJ
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.
Orbital symmetry and electron correlation in NaxCoO2
(2006-05-01)
Wu, WB
;
Huang, DJ
;
Okamoto, J
;
Lin, HJ
;
Chou, FC
We present measurements of polarization-dependent soft X-ray absorption on NaxCoO2. The results reveal that the electronic states determining the low-energy excitations of NaxCoO2 have predominantly a(1g) symmetry with significant O 2p character. A large transfer of spectral weight observed in O 1s X-ray absorption provides spectral evidence for strong electron correlations in NaxCoO2 with the Na doping higher than half. For the Na concentration less than half, our measurements of O 1s absorption suggest that Na2CoO2 exhibits band-like electronic character. (c) 2006 Published by Elsevier B.V.