Narrow Results

Cuprate-planes are not necessary and essential for high-temperature superconductivity: doped Sr₂YRuO₆ superconducts fully at 23 K in its SrO layers once the Ru stops librating (the material begins superconducting at ≈ 49K). GdSr₂Cu₂RuO₈ superconducts near 45 K in its SrO layers, not in its cuprate-planes. By examining the charge transfer, we find that T_c increases with the number of layers n and with pressure p in the HgBa₂Ca_n-1Cu_nO_2n+2 compounds, as does the charge in the BaO layers (and not the charge in the cuprate-planes), indicating that the superconductivity is in the BaO layers. Four superconductors, including PrBa₂Cu₃O₇, were successfully predicted to superconduct not in their cuprate-planes, but in their BaO or SrO layers. The original claims that the superconductivity resides primarily in the cuprate-planes are invalid.

The magnetic ion Gd⁺³, having L = 0 and J ≠ 0, is unsplit by crystal fields and, unlike the other trivalent L ≠ 0 rare-earth ions (which are crystal-field split), is a pair-breaker in high-temperature superconductors. Consequently two-layer compounds with Gd (i.e., Gd_2-zCe_zCuO₄ and Ba₂GdRu_1-uCu_uO₆) do not superconduct, but their sister compounds without unsplit and pair-breaking Gd, do superconduct (e.g., Nd_2-zCe_zCuO₄, with crystal-field split Nd, and Sr₂YRu_1-uCu_uO₆, with L = 0 Y, both superconduct). The superconductivity clearly originates in the oxygen of the SrO or BaO layers, or in interstitial oxygen, not in the CuO₂ planes.