GEOMETRICAL BARRIERS IN HIGH-TEMPERATURE SUPERCONDUCTORS

A theoretical description of vortex dynamics in thin flat samples is derived and is found to compare favorably with experimental results. In perpendicular applied magnetic field the vortex penetration is delayed significantly due to the presence of a potential barrier of geometrical origin. This novel geometrical barrier effect results in hysteretic magnetization and in the existence of an irreversibility line in the absence of bulk pinning. Among the unique characteristics of the barrier are a vortex concentration in the center of the sample and a zero-field peak in the magnetization loops.