Reentrant pinning effect in the vortex liquid phase of a quasi-two-dimensional Bi2Sr2CaCu2O8/Bi2Sr2CuO6 multilayer with columnar defects - art. no. 020504

The ab-plane magnetoresistance R(H) is studied for an extremely anisotropic Bi2Sr2CaCu2O8/Bi2Sr2CuO6 multilayer with columnar defects (CD's). In a wel l-defined range of H and T, R(H) exhibits slope changes due to the pinning of vortices by CD's. Angular measurements reveal that the dissipation is st ill determined by the motion of two-dimensional pancakes proving that the o ccurrence of this feature is controlled by a field-driven competition betwe en intralayer vortex repulsion and entropy. We draw the contour of a reentr ant pinned liquid region in the (H,T) phase diagram where CD's decrease the dissipation.