Electron-doped superconductivity at 40 K in the infinite-layer compound Sr_1–yNd_yCu0₂

Abstract

THE known copper oxide superconductors all have intergrowth structures consisting of superconducting layers of fixed oxygen content alternating with non-superconducting oxide layers. Siegrist et al.¹ reported the synthesis of the 'infinite-layer' parent compound of the copper oxide superconductor—a structure comprising CuO₂ planes separated only by calcium and strontium atoms, with the composition Ca₀₈₆Sr₀₁₄CuO₂. Although this compound has not been made to superconduct, here we show that the isostructural compound Sr_1–yNd_yCuO₂, in which the substitution of neodymium for strontium adds electrons to the CuO₂ planes, is superconducting at 40 K. The difference in dopant type seems to distinguish this superconductor from the superconductivity found in a multiphase sample of nominal composition Sr_1–yBa_yCuO₂ by Takano et al.², in an independent study.