Evidence of the direct role of dopant oxygen in high‐temperature superconductivity

Abstract

The critical compositions u_c of Cu‐site Ni and Zn necessary to destroy superconductivity in Nd_2‐zCe_zCuO₄, La_2‐ß ,Sr _ß CuO₄, Bi₂Sr₂CaCu₂O₈, Bi_1–8Pb_0.2Sr₂Ca₂Cu₃O₁₀, YBa₂Cu₃O₇ and YBa₂Cu₄O₈ scale approximately exponentially with the distance of the impurity sites from the dopant oxygen in the charge‐reservoir regions of the crystals. This indicates that the superconducting condensates are primarily in the charge reservoirs, where they are directly controlled by dopant oxygen—not in the cuprate planes where they would be remotely controlled, as is assumed by all cuprate‐plane theories. The critical temperatures also show a trend with the same distance, suggesting that the transition temperature may be increased by fabricating superconductors whose charge reservoirs lie farther from the cuprate planes.