Superconductors, high penetration depth

Fig. 16.48 This residual density of states was pointed out theoretically to appear in the unitarity limit scattering by non-magnetic impurities in p- or d-wave superconductors in a heavy fermion study.49 From this result it became possible to explain the BCS-like temperature dependence of the penetration depth, A,50 which supported strongly the. 9-wave pairing model in high-7 , superconductors at an early stage, in terms of the d-wave + impurity model.51 53...

The superconductor is a perfect diamagnet and the magnetic field is expelled by shielding currents which flow on the surface of the superconductor and penetrate only a small distance (10 cm) into the bulk of the specimen. The surface currents are just high enough to cancel the magnetic field in the interior. The distance the field penetrates is called the penetration depth A. As the field is increased, the field begins to penetrate the sample. 

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