Nonlocal Effects on the Magnetic Penetration Depth in d-Wave Superconductors

We show that, under certain conditions, the low temperature behavior of the magnetic penetration depth λ(T) of a pure d -wave superconductor is determined by nonlocal electrodynamics and, contrary to the general belief, the deviation Δλ(T)=λ(T)-λ (0) is proportional to T2 and not T . We predict that the Δλ(T)∝T2 dependence, due to nonlocality, should be observable experimentally in nominally clean high-Tc superconductors below a crossover temperature T*=(ξ0/λ0)Δ0∼1 K. Possible complications due to impurities, surface quality, and crystal axes orientation are discussed. copyright 1997 The American Physical Society