Order-parameter symmetries in high-temperature superconductors

We present two representations of the order-parameter (OP) eigenfunctions for tetragonal cuprate superconductors, and for orthorhombic YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{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{sub x{sup 2}-y{sup 2}}-wave component. We propose a c-axis twist tetracrystal ring experiment. (c) 2000 The American Physical Society.