Impurity effects on the spin excitation spectra in a d-wave superconductor

TL;DR

This paper investigates how nonmagnetic impurities affect the spin excitation spectra in a d-wave superconductor, revealing shifts and broadening of resonance peaks and maintaining gap features, aligning with experimental observations.

Contribution

It introduces a self-consistent t-matrix approach to analyze impurity effects on spin excitations in d-wave superconductors, highlighting the roles of impurity self-energy and vertex corrections.

Findings

Impurity self-energy shifts resonance peaks to lower frequencies.

Impurity vertex correction broadens spectral features.

Gaplike features persist despite impurity effects.

Abstract

The effects of nonmagnetic impurity on the spin excitation spectra in a $d_{x^2-y^2}$-wave superconductor are examined, using the self-consistent $t$-matrix approximation. It is shown that the impurity self-energy acts 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. Incorporating these two effects, we find that the result is in qualitative agreement with experiments on YBa_{2}(Cu_{1-x}Zn_{x})_{3}O_{6+y}.