IMPURITY EFFECTS ON THE SPIN EXCITATION-SPECTRA IN A D-WAVE SUPERCONDUCTOR

The effects of nonmagnetic impurity on the spin excitation spectra in a d(x)2(-y)2-wave superconductor are examined, using the self-consiste nt t-matrix approximation. It is shown that the impurity self-energy a cts to shift the position of the resonance peak to low frequencies and broaden the peak. While the impurity vertex correction causes a broad spectral weight in the spin gap at the impurity concentrations where no clear resonance peak is observed. The gaplike feature still remains in low frequency region upon the introduction of impurities. Incorpor ating these two effects, we find that the result is in qualitative agr eement with experiments on YBa2(Cu1-xZnx)(3)O6+y.