EFFECT OF STRONG SCATTERING ON THE LOW-TEMPERATURE PENETRATION DEPTH OF A D-WAVE SUPERCONDUCTOR

For a pure superconductor in a d-wave-like state at temperatures T well below the critical temperature T(c), the deviation DELTAlambda of the penetration depth from its zero-temperature value lambda(0) is proportional to T. When the concentration ni of strongly scattering impurities is nonzero, DELTAlambda is-proportional-to T(n), where n=2 for T < T* << T(c) and n=1 for T* < T << T(c). The crossover temperature T* and the increase in lambda(0) scale as square-root n(i) up to logarithmic corrections when resonant scattering is dominant. We argue that this case is relevant to recent measurements on YBa2Cu3O7-delta and present specific results for a model pairing state with d(x2-y2) symmetry.