The behavior of the penetration depth λ at low temperatures is an important probe of the symmetry of the order parameter in superconductors. For this reason, the penetration depth in the high-${\mathit{T}}_{\mathit{c}}$ oxide has been the focus of much recent experimental and theoretical attention. In this paper we provide detailed results for the behavior of λ at T=0, as a function of impurity scattering, for an unconventional order parameter.

• Received 22 September 1993

DOI:https://doi.org/10.1103/PhysRevB.49.3544