Superconducting Coherence and the Helicity Modulus in Vortex Line Models

TL;DR

This paper introduces a modified vortex line model for 3D superconductors that includes k=0 excitations, providing a new criterion for superconducting coherence and analyzing vortex lattice melting via Monte Carlo simulations.

Contribution

It develops a formula for the k=0 helicity modulus based on vortex loop fluctuations and applies it to study vortex lattice melting in YBCO.

Findings

The k=0 helicity modulus effectively indicates superconducting coherence.

Monte Carlo simulations reveal details of vortex lattice melting.

The model captures vortex loop fluctuations influencing superconductivity.

Abstract

We show how commonly used models for vortex lines in three dimensional superconductors can be modified to include k=0 excitations. We construct a formula for the k=0 helicity modulus in terms of fluctuations in the projected area of vortex loops. This gives a convenient criterion for the presence of superconducting coherence. We also present Monte Carlo simulations of a continuum vortex line model for the melting of the Abrikosov vortex lattice in pure YBCO.