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Turkish Journal of Physics

Contraction of Atomic Orbitals in the Oxygen Anion Network and Superconductivity in Metal Oxide Compounds

I. O. KULIK

DOI

-

Abstract

Anion network in the CuO_2 plane of metal-oxide compound is considered as an intrinsic-hole metal with holes rather than electrons comprising a Fermi liquid immersed in the background of negative ~O^{2-}~ ions. Due to the contraction of p-orbital of oxygen as a result of occupation by a hole, hole hopping between nearest neighbor sites (i,j) is dependent upon hole occupation as t_{ij,\sigma} = t_0 + Vn_{i,-\sigma}n_{j,-\sigma} + W(n_{i,-\sigma}+n_{j,-\sigma}). Coupling parameters $W$ and V (additive and multiplicative "contraction interaction" terms) result in the binding of holes into singlet, on-site configuration, or into triplet, nearest-neighbor-site configuration, due to W and V respectively. In the weak coupling limit, W results in the BCS type of superconductive pairing (singlet, s-wave), whereas multiplicative contraction $V$ provides for either singlet, $d$-wave, or triplet, p-wave-like pairing states. It is concluded that the latter state may result in a plausible mechanism for high-T_c superconductivity in metal oxide compounds. The superconducting $p$-phase is shown to be in accord with recently published symmetry tests of the order parameter in oxides

First Page

627

Last Page

654

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