Disorder in two dimensional Josephson junctions

TL;DR

This paper develops a theoretical framework for understanding phase behavior in large-area two-dimensional Josephson junctions, revealing four distinct phases influenced by disorder, thermal fluctuations, and external fields.

Contribution

It introduces a novel free energy model incorporating disorder and fluctuations, and identifies four phases using replica symmetry breaking methods.

Findings

Four distinct phases identified: disordered, Josephson ordered, glass, and coexistence phase.

Critical current near the glass transition scales as (area)^{-s+1/2}.

Results explain junction ordering at temperatures below the bulk critical temperature in high T_c junctions.

Abstract

An effective free energy of a two dimensional (i.e. large area) Josephson Junctions is derived, allowing for thermal fluctuations, for random magnetic fields and for external currents. We show by using replica symmetry breaking methods, that the junction has four distinct phases: disordered, Josephson ordered, a glass phase and a coexisting Josephson order with the glass phase. Near the coexistence to glass transition at s=1/2 the critical current is ~ (area)^{-s+1/2} where s is a measure of disorder. Our results may account for junction ordering at temperatures well below the critical temperature of the bulk in high T_c trilayer junctions.