SHORT COHERENCE LENGTH IN CUPRATE SUPERCONDUCTORS

Abstract

We investigated very short coherence lengths, ξCu in the high transition temperature superconductors. It is shown that phonon-enhanced spin fluctuations drive this superconductivity once more, as was as suggested by us [Phys. Rev. B61, 4289]. The short coherence length, ξCu in cuprate superconductors results from the giant superconducting gap. The superconducting gap, Δ happens at the top of the valence band where the Fermi level is located nearly upon the top of the valence band because of the low occupation of the conduction band. It is shown the effective superconducting gap is nearly the band gap, Eg where Cooper-type superconducting condensations are available with energy width, Eg+Δ≃Eg.