ROLE OF ANISOTROPIC IMPURITY SCATTERING IN ANISOTROPIC SUPERCONDUCTORS

A theory of nonmagnetic impurities in an anisotropic superconductor in cluding the effect of anisotropic (momentum-dependent) impurity scatte ring is given. It is shown that for a strongly anisotropic scattering the reduction of the pair-breaking effect of the impurities is large. For a significant overlap between the anisotropy functions of the scat tering potential and that of the pair potential and for a large amount of anisotropic scattering rate in impurity potential the superconduct ivity becomes robust vis-a-vis impurity concentration. The implication s of our result for YBCO high-temperature superconductor are discussed . The experimental data of electron irradiation-induced T-c suppressio n [Phys. Rev. B 50, 15 967 (1994)] are understood quantitatively and a good qualitative agreement with the ion (Ne+) damage and Pr substitut ion-induced T-c decrease data [Phys. Rev. B 50, 3266 (1994)] is obtain ed.