EFFECT OF ANISOTROPY ON UNIVERSAL TRANSPORT IN UNCONVENTIONAL SUPERCONDUCTORS

We investigate the universal electronic transport for a mixed d(x2-y2) + s-wave superconductor in the presence of an anisotropic elliptical Fermi surface. Similar to the universal low-temperature transport pred icted in a d(x2-y2)-wave superconductor with a circular Fermi surface, anisotropic universal features are found in the low-temperature micro wave conductivity and thermal conductivity in the anisotropic system. The effects of anisotropy on the penetration depth, impurity induced T -c suppression, and the zero-frequency density of states are also cons idered. While a small amount of anisotropy can lead to a strong suppre ssion of the effective scattering rate, and hence the density of state s at zero frequency, experimental data suggest that large effects are restored by a negative s-component gap admixture.