Decoupling and melting in a layered superconductor

TL;DR

This study uses 3D simulations to investigate the phase transitions in layered superconductors, identifying distinct melting and decoupling temperatures with different transition characteristics.

Contribution

It provides new insights into the nature of vortex lattice melting and layer decoupling, highlighting their temperature dependence and the impact of anisotropy.

Findings

Decoupling is a first order transition with entropy ~0.25-0.4 k_B/pancake.

Melting shows no clear thermodynamic signature, possibly a crossover.

Increased anisotropy reduces the temperature gap between melting and decoupling.

Abstract

We report results for a 3D simulation of a layered superconductor. There are two significant temperatures. The first corresponds to melting of the vortex lattice in the a-b plane (T_ab) and the second to decoupling of the layers (T_dc) with T_ab \le T_ dc. The decoupling is found to be a first order transition with an associated entropy of ~0.25-0.4 k_B/pancake. The melting has no obvious thermodynamic signature, and could be a crossover. The width of the intermediate regime T_ab<T<T_dc, decreases with increasing anisotropy such that for the more anisotropic system we cannot distinguish the melting and decoupling temperatures.