EFFECTS OF NONMAGNETIC IMPURITY ATOMS ON THE SPIN-DENSITY-WAVE MODEL OF HIGH-TEMPERATURE SUPERCONDUCTIVITY

We present the effects of nonmagnetic impurity atoms in high-temperature superconductivity. We employ the perturbation expansion in the weak-scattering region for a model of superconductivity induced by spin-density-wave (SDW) fluctuations. We assert that there are two competing effects: (i) The impurity atoms reduce the SDW gap, thus increasing the attractive interaction between holes and consequently increasing the superconducting gap SC; (ii) the nonmagnetic impurity atoms in this model apparently behave as though they are magnetic, thus causing pair breaking and accordingly reducing SC. We find that the latter effect is more dominant than the former; thus altogether the superconducting gap SC is reduced by the nonmagnetic impurity atoms. We also discuss the relationship to the experimental results concerning the reduction of the critical temperature due to the nonmagnetic impurity atoms. © 1990 The American Physical Society.