Measurements of the resistivity, magnetoresistance, and penetration depth were made on films of La1.85Sr0.15CuO4, with up to 12 at. % of Zn substituted for the Cu. The results show that the quadratic temperature dependence of the inverse square of the penetration depth, indicative of d-wave superconductivity, is not affected by doping. The suppression of superconductivity leads to a metallic no...

We investigate the doping dependence of the penetration depth versus temperature in electron-doped Pr(2-x)Ce(x)CuO(4-delta) using a model which assumes the uniform coexistence of (mean-field) antiferromagnetism and superconductivity. Despite the presence of a d(x2-y2) pairing gap in the underlying spectrum, we find nodeless behavior of the low-T penetration depth in the underdoped case, in acco...

– We show that the inclusion of effects beyond Migdal’s limit in the electron-phonon interaction naturally leads to an isotope effect for the effective mass m∗ of the charge carriers even much before reaching the polaron limit. This is the situation already considered in our approach to nonadiabatic superconductivity [7]. Such a result provides a scenario different from the polaronic one for th...

The effect of smooth inhomogeneities near a superconductor boundary on the magnetic penetration depth λ is studied with emphasis on the proximity-induced spatial dependence of the Cooper pair amplitude. The influence of surface pair breaking or pair formation on λ is described within the Ginzburg-Landau theory, with no model assumptions, for both strongly type-II and strongly type-I homogeneous...

We examine recent results on measurements of the magnetic penetration depth in cuprate superconductors, with particular emphasis on our results obtained with the microstrip and parallel-plate resonator techniques. The results show that the magnetic penetration depth temperature dependence in YBa2Cu307-a is not consistent with a simple scaled weak-coupled BCS temperature dependence. We present t...