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

TL;DR

This paper investigates how planar magnetic imperfections affect the low-temperature properties of d-wave cuprate superconductors, revealing different scattering regimes and providing evidence for dirty d-wave superconductivity through neutron scattering data.

Contribution

It introduces a detailed analysis of impurity effects on quasiparticle spectra and spin dynamics in cuprate superconductors, distinguishing between quasi-one-dimensional and two-dimensional scattering regimes.

Findings

Impurities induce low-energy quasiparticles with anisotropic spectra near nodes.

La2-xSrxCuO4 is in the quasi-1D scattering regime for impurity concentrations >0.16%.

YBCO7 likely remains in the true 2D scattering regime for Zn concentrations <1.6%.

Abstract

We consider the influence of planar ``magnetic" imperfections which destroy the local magnetic order, such as Zn impurities or $Cu^{2+}$ 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 $La_{2-x}Sr_xCuO_4$ 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 $La_{1.86}Sr_{0.14}CuO_4$ 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.