Disorder Effects on the Intrinsic Nonlinear Current Density in ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}$

We present harmonic generation measurements of the intrinsic nonlinear current density j
₂
of YBa
₂
Cu
₃
O
_7-delta
(YBCO) films at temperatures close the T
_c
. Experiments on a range of different quality samples allow us to extract the dependence of j
₂
on the penetration depth of the superconductor. In order to model these results, we calculate the intrinsic nonlinear current response of d
_x

²

_-y

²
-wave superconductors in the Meissner regime in the presence of nonmagnetic impurities within the self-consistent T-matrix approximation.