Pre-melting of crossing vortex lattices

TL;DR

This paper provides a theoretical explanation for the pre-melting phenomenon in layered superconductors with crossing vortex lattices, highlighting the role of vortex density in melting behavior.

Contribution

It introduces a numerical method to determine the vortex cage potential and identifies vortex density as the key factor in pre-melting.

Findings

Pre-melting occurs when thermal energy causes vacancy-interstitial proliferation.

Increased pancake vortex density in certain planes drives pre-melting.

The incommensurate structure of vortices is not the main cause of pre-melting.

Abstract

The pre-melting of high vortex density planes observed recently in layered superconductors in tilted magnetic field is explained theoretically. Based on the structural information of the crossing lattices of pancake and Josephson vortices the effective vortex cage potential at different lattice sites is determined numerically. Melting takes place when the thermal energy allows proliferation of vacancy-interstitial pairs. It is found that the increased density of pancake vortex stacks in the planes containing Josephson vortices, rather than their incommensurate structure, is the main cause for pre-melting.