Phase Transitions of the Flux Line Lattice in High-Temperature Superconductors with Weak Columnar and Point Disorder

TL;DR

This paper investigates how weak columnar and point disorder influence vortex-lattice phase transitions in high-temperature superconductors, revealing opposite effects on the melting line and the role of replica symmetry breaking in vortex glass formation.

Contribution

It introduces a simplified cage model to analyze the combined effects of thermal fluctuations and quenched disorder on vortex-lattice transitions, highlighting the contrasting impacts of different disorder types.

Findings

Columnar and point disorder have opposite effects on the melting line.

Replica symmetry breaking is involved in the vortex glass transition.

The model maps to a quantum particle in a harmonic + random potential.

Abstract

We study the effects of weak columnar and point disorder on the vortex-lattice phase transitions in high temperature superconductors. The combined effect of thermal fluctuations and of quenched disorder is investigated using a simplified cage model. For columnar disorder the problem maps into a quantum particle in a harmonic + random potential. We use the variational approximation to show that columnar and point disorder have opposite effect on the position of the melting line as observed experimentally. Replica symmetry breaking plays a role at the transition into a vortex glass at low temperatures.