Low temperature magnetic penetration depth in d-wave superconductors

We briefly review the experimental results of the low temperature magnetic penetration depth λ(T) of d-wave superconductors. In very clean high-Tc superconductors (HTSC) the low temperature in-plane penetration depth λ‖(T) varies linearly with T. A weaker power law temperature dependence is found for the out-of-plane penetration depth λ⊥(T) in most of HTSC. In the organic superconductors κ-(BEDT-TTF)2X [X=Cu(NCS)2, Cu[N(CN)2]Br] and slightly dirty HTSC λ‖∝bT2/(T*+T), where T∗≈ΓΔ0 is deduced from an impurity scattering model. In clean CeCoIn5 a crossover from linear to quadratic temperature behavior at low T was interpreted as the first evidence for nonlocal effects in a d-wave superconductor.