EFFECT OF IMPURITY SCATTERING ON A (D+S)-WAVE SUPERCONDUCTOR

Recent measurements of the surface impedance in YBa2Cu3O7-delta Single crystals show large in-plane anisotropy which implies that orthorhombicity due to the Cu-O chains is not small. In addition, the controversy between the d-wave and the s-wave order parameter persists. In the framework of the orthorhombic symmetry an order parameter with (d+s)-wave symmetry is considered in an attempt to understand current experimental results. We provide a detailed study of the characteristics of such an order parameter in the low-temperature behavior of the penetration depth, the density of states, and the T-c suppression in the presence of nonmagnetic impurity scattering. The results are discussed in comparison with the d-wave and the anisotropic s-wave cases.