Bernoulli potential in type-I and weak type-II superconductors: I. Surface charge

The electrostatic potential close to the surface of superconductors in the Meissner state is discussed. We show that beside the Bernoulli potential, the quasiparticle screening, and the thermodynamic contribution due to Rickayzen, there is a non-local contribution which is large for both type-I and weak type-II superconductors.Comment: 7 pages, 4 figure

Strong 3D correlations in vortex system of Bi2212:Pb

The experimental study of magnetic flux penetration under crossed magnetic fields in Bi2212:Pb single crystal performed by magnetooptic technique (MO) reveals remarkable field penetration pattern alteration (flux configuration change) and superconducting current anisotropy enhancement by the in-plane field. The anisotropy increases with the temperature rise up to $T_m = 54 \pm 2 K$. At $T = T_m$ an abrupt change in the flux behavior is found; the correlation between the in-plane magnetic field and the out-of-plane magnetic flux penetration disappears. No correlation is observed for $T > T_m$. The transition temperature $T_m$ does not depend on the magnetic field strength. The observed flux penetration anisotropy is considered as an evidence of a strong 3D - correlation between pancake vortices in different CuO planes at $T < T_m$. This enables understanding of a remarkable pinning observed in Bi2212:Pb at low temperatures.Comment: 8 pages, 9 figure

BARRIERS TO FLUX ENTRY AND EXIT IN SEMI-REVERSIBLE TYPE II SUPERCONDUCTORS

Un échantillon refroidi dans un champ constant montre, après qu'un pulse de chaleur ait induit une expulsion de flux, une barrière qui s'oppose à la sortie de tourbillons comparable à celle qui s'oppose à leur entrée.A sample cooled in a static H exhibits, after heat pulse induced flux expulsion, a barrier against flux exit comparable to that opposing flux entry