Superconducting Properties of Copper Oxide High-Temperature Superconductors

Abstract

The equations for the magnon pairing theory of high-temperature copper-oxide-based superconductors are solved and used to calculate several properties, leading to results for specific heat and critical magnetic fields consistent with experimental results. In addition, the theory suggests an explanation of why there are two sets of transition temperatures (Tcapprox 90 K and Tcapprox 55 K) for the Y1Ba2Cu3O6+x class of superconductors. It also provides an explanation of why La2-xSrxCuO4 is a superconductor for only a small range of x (and suggests an experiment to independently test the theory). These results provide support for the magnon pairing theory of high-temperature superconductors. On the basis of the theory, some suggestions are made for improving these materials. The agreement with experiment for various properties predicted by using the magnon pairing model of superconductivity provides strong support for the validity of this model for the Cu--O systems. All quantities are related to the fundamental parameters of the system (Jdd, JOCu, band structure). Some approximations have been made in the solutions to these equations. Nevertheless, the fundamental parameters are well defined, and hence improved calculational approximations will eventually lead to precise predictions of all properties. In this theory, the superconducting properties are related to fundamental structural, chemical, and physical properties, allowing one to use qualitative reasoning in contemplating how to improve the properties.