ELECTRON-DOPED SUPERCONDUCTIVITY AT 40-K IN THE INFINITE-LAYER COMPOUND SR1-YNDYCUO2

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 Ca0.86Sr0.14CuO2. Although this compound has not been made to superconduct, here we show that the isostructural compound Sr(1-y)Nd(y)CuO2, 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-y)Ba(y)CuO2 by Takano et al. 2, in an independent study.