CMT63
The Nonlinear Meissner Effect in Unconventional Superconductors
Author(s):
D. Xu, S.-K. Yip and J. A. Sauls
Comments: 30 pages with 16 figures
Journal:
Physical Review B, 51, 16233 (1995)
[DOI]
Abstract:
We examine the long-wavelength
current response in anisotropic superconductors and show how the field-dependence
of the Meissner penetration length can be used to detect the structure
of the order parameter. Nodes in the excitation gap lead to a nonlinear
current-velocity constitutive equation at low temperatures which is distinct
for each symmetry class of the order parameter. The effective Meissner
penetration length is linear in H and exhibits a characteristic
anisotropy for fields in the ab-plane that is determined by the
positions of the nodes in momentum space. The nonlinear current-velocity
relation also leads to an intrinsic magnetic torque for in-plane fields
that are not parallel to a nodal or antinodal direction. The torque scales
as H3 for
T -> 0 and has a characteristic angular
dependence. We analyze the effects of thermal excitations, impurity scattering
and geometry on the current response of a
dx2-y2superconductor,
and discuss our results in light of recent measurements of the low-temperature
penetration length and in-plane magnetization of single-crystals of
YBa2Cu3O7-y
and LuBa2Cu3O7-y.
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