Order-parameter symmetries in high-temperature superconductors

Abstract

We present two representations of the order-parameter (OP) eigenfunctions for tetragonal cuprate superconductors, and for orthorhombic ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ and ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ (BSCCO). Recent BSCCO c-axis twist Josephson junction experiments of Li et al. demonstrate that the tunneling is strongly incoherent, and that the OP contains an isotropic s-wave component, but not any ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-wave component. We propose a c-axis twist tetracrystal ring experiment.