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

TL;DR

This study investigates how reducing the size of nanocrystalline vortex matter in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ affects its phase transition lines and entropy jump, revealing size-dependent shifts and depletion effects.

Contribution

It demonstrates that first-order transition lines persist in extremely small vortex systems and reveals how their properties change with size, especially the entropy jump and transition fields.

Findings

First-order transition lines persist in systems with fewer than a hundred vortices.

The vortex solidification transition temperature remains unchanged with size reduction.

The entropy jump decreases as the system size diminishes.

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.