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Electronic structure of high-Tc Ba0.6K0.4BiO3 by x-ray photoelectron spectroscopy

Hegde, MS and Barboux, P and Tarascon, JM and Venkatesan, T and Chang, CC and Wu, XD and Inam, A (1989) Electronic structure of high-Tc Ba0.6K0.4BiO3 by x-ray photoelectron spectroscopy. In: Physical Review B: Condensed Matter, 39 (7). pp. 4752-4755.

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We have investigated the electronic structure of Ba1-xKxBiO3 (0<x<0.4) by x-ray photoelectron spectroscopy. The Bi(4f) core levels show a normal valency of +3 as in Bi2O3 and we find no evidence for the disproportionation of Bi4+ to Bi3+ and Bi5+. Instead, we find that BaBiO3 has mixed valent O2- and O1- ions. As the potassium doping is increased, the binding energy of the O2- ions in the O(1s) photoelectron spectra steadily decreases from 529.7 to 528.8 eV. The effect of lowering the O(1s) binding energy is to raise the O(2p) band towards EF and at the superconducting composition a finite density of O(2p) states is observed near EF. Similarly, the Ba(5p) binding energies decrease with potassium doping, indicating increased metallicity. The behavior of the O(1s), Ba(5p), and the valence band resembles that of all the cuprate superconductors and we conclude that in all these oxide superconductors, a hole in the (filled) O(2p) band is the carrier responsible for superconductivity, which predicts hole conduction in the Ba-K-Bi-O and Ba-Pb-Bi-O systems.

Item Type: Editorials/Short Communications
Publication: Physical Review B: Condensed Matter
Publisher: The American Physical Society
Additional Information: Copyright of this article belongs to The American Physical Society.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 26 Aug 2010 10:17
Last Modified: 19 Sep 2010 06:15
URI: http://eprints.iisc.ac.in/id/eprint/31550

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