Superconductivity, Spin Gaps and Luttinger Liquids in a Class of Cuprates

A homologous series of cuprates, Srn -1 Cun + 1 O2n, formed by introducing a parallel array of planar defects into the infinite-layer cuprate, SrCuO2, have been reported by Takano et al. In each CuO2 plane line defects consisting of CuO double chains result. An analysis of the electronic properties of such planes demonstrates that the stoichiometric compounds with n = 3, 7, 11,... will be frustrated quantum antiferromagnets and spin liquids. When lightly doped with holes the spin gap will remain and singlet superconductivity should occur on a separate but high temperature scale. This prediction may shed new light on the origin of the separate energy scales for the spin gap and superconductivity in other lightly doped cuprates.