Variational theory of flux-line liquids

TL;DR

This paper develops an improved variational theory for flux line liquids, analyzing how confinement of flux line fluctuations varies with temperature and identifying a transition to freely fluctuating vortices at high temperatures.

Contribution

It introduces a refined variational approach to flux line liquids, extending previous models and detailing the temperature dependence of vortex confinement.

Findings

Massive confinement term decreases with temperature

Vortices become freely fluctuating elastic lines at high temperatures

Enhanced understanding of flux line fluctuation behavior

Abstract

We formulate a variational (Hartree like) description of flux line liquids which improves on the theory we developed in an earlier paper [A.M. Ettouhami, Phys. Rev. B 65, 134504 (2002)]. We derive, in particular, how the massive term confining the fluctuations of flux lines varies with temperature and show that this term vanishes at high enough temperatures where the vortices behave as freely fluctuating elastic lines.