The Influence of Magnetic Imperfections on the Low Temperature Properties of D-wave Superconductors

Abstract

We consider the influence of planar ``magnetic" imperfections which destroy the local magnetic order, such as Zn impurities or $C{u}^{2+}$ vacancies, on the low temperature properties of the cuprate superconductors. In the unitary limit, at low temperatures, for a $d_{x^2-y^2}$ pairing state such imperfections produce low energy quasiparticles with an anistropic spectrum in the vicinity of the nodes. We find that for the $L{a}_{2-x}S{r}_{x}Cu{O}_4$ system, one is in the {\em quasi-one-dimensional} regime of quasiparticle scattering, discussed recently by Altshuler, Balatsky, and Rosengren, for impurity concentrations in excess of $\sim 0.16\%$ whereas YBCO${}_7$ appears likely to be in the true 2D scattering regime for Zn concentrations less than $1.6\%$. We show the neutron scattering results of Mason et al. \cite{Aeppli} on $L{a}_{1.86}S{r}_{0.14}Cu{O}_4$ provide strong evidence for ``dirty d-wave" superconductivity in their samples. We obtain simple expressions for the dynamic spin susceptibility and ${}^{63}Cu$ spin-lattice relaxation time, ${}^{63}{T}_1$, in the superconducting state.

10 pages; revtex; Los Alamos preprint LA-UR-94-534