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
∼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.