Explanation of high-temperature superconductivity without cuprate planes

Abstract

The superconducting hole condensate resides in the SrO planes, or in the BaO planes, or in the interstitial regions of high-temperature perovskite superconductors, depending upon the crystal structure. Supporting evidence includes the following: firstly, PrBa₂Cu₃O₇ superconducts in its BaO layers, and not in its cuprate planes; secondly, the similarity of the layer charges for YBa₂Cu₃O_x and PrBa₂Cu₃O_x indicates that both materials superconduct in their BaO layers; thirdly, Gd_2-zCe_zSr₂Cu₂TiO₁₀, Pr_2-zCe_zSr₂Cu₂NbO₁₀ and Eu_2-zCe_zSr₂Cu₂TiO₁₀ all superconduct in their SrO layers, and not in their cuprate planes; and fourthly, the superconducting hole condensate for Cu-doped Sr₂YRuO₆ (a material with no cuprate planes to better than 1%) must reside in its SrO layers.