Size-induced depression of first-order transition lines and entropy-jump in extremely-layered nanocrystalline vortex matter

Abstract

We detect the persistence of the solidification and order-disorder first-order transition lines in the phase diagram of nanocrystalline Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ vortex matter down to a system size of less than hundred vortices. The temperature-location of the vortex solidification transition line is not altered by decreasing the sample size although there is a depletion of the entropy-jump at the transition with respect to macroscopic vortex matter. The solid order-disorder phase transition field moves upward on decreasing the system size due to the increase of the surface-to-volume ratio of vortices entailing a decrease on the average vortex binding energy.