On the melting of the nanocrystalline vortex matter in high-temperature superconductors

TL;DR

This paper uses Monte Carlo simulations to study vortex matter in high-temperature superconductors, revealing a two-step melting process and phase transitions consistent with experimental observations.

Contribution

The study introduces a detailed simulation approach including both electromagnetic and Josephson interactions, and proposes a theoretical model matching observed phase behavior.

Findings

Identification of nanocrystalline, nanoliquid, and liquid phases

Observation of a two-step melting process

Enhanced structure factor prior to melting

Abstract

Multilevel Monte Carlo simulations of the vortex matter in the highly-anisotropic high-temperature superconductor Bi$_2$Sr$_2$CaCu$_2$O$_8$ were performed. We introduced low concentration of columnar defects satisfying $B_\phi\le B$. Both the electromagnetic and Josephson interactions among pancake vortices were included. The nanocrystalline, nanoliquid and homogeneous liquid phases were identified in agreement with experiments. We observed the two-step melting process and also noted an enhancement of the structure factor just prior to the melting transition. A proposed theoretical model is in agreement with our findings.