MAXIMUM PINNING ENERGY OF VORTICES IN ANISOTROPIC AND LAYERED SUPERCONDUCTORS

In type-II superconductors the pinning force which determines the critical current density J(c), and the pinning energy U which determines thermally activated depinning, in principle are different quantities. Long pinning channels generated by high-energy heavy-ion irradiation, in YBCO can enhance both J(c) and U, but in the strongly layered BSCCO they may enhance J(c) without enhancing U, since the pancake vortices in the layers depin individually. This is the reason why in BSCCO flux creep is large down to rather low temperatures.