Vortex-Loop Unbinding and Flux-Line Lattice Melting in Superconductors

TL;DR

This paper investigates how vortex-loop unbinding influences flux-line lattice melting in type-II superconductors, revealing different behaviors based on anisotropy levels and their effects on phase coherence.

Contribution

It introduces a detailed analysis of vortex-loop unbinding phenomena and their impact on flux-line lattice melting in superconductors with varying anisotropy.

Findings

Phase coherence along c-axis is lost at T_V > T_M for moderate anisotropy.

For large anisotropy, phase coherence is lost at T_V < T_M.

Vortex-loop unbinding mechanisms depend on anisotropy levels.

Abstract

We study the interplay between a novel vortex-loop unbinding in finite magnetic field at T=T_V and flux-line lattice (FLL) melting at T=T_M in type-II superconductors. The FLL melts due to nucleation of vortex loops parallel to c-axis, connected to flux lines. For moderate anisotropy, phase coherence along c-axis is lost at T_V > T_M due to an ab-plane vortex-loop unbinding with loops located close to thermal FLL fluctuations. For large anisotropy, phase coherence along c-axis is lost at T_V < T_M due to nucleation of ab-plane vortex-loops uncorrelated to flux lines.