Vortex Line Fluctuations in Model High Temperature Superconductors

TL;DR

This study uses Monte Carlo simulations of the 3d XY model to investigate vortex line fluctuations in high-temperature superconductors, revealing two phase transitions and an intermediate phase with unique properties.

Contribution

It introduces a detailed simulation-based analysis of vortex line phases, identifying an intermediate disentangled vortex liquid phase with mixed superconducting and normal behaviors.

Findings

Identified two sharp phase transitions in vortex line behavior.

Discovered an intermediate vortex liquid phase with partial superconductivity.

Characterized vortex line entanglement and loop excitations across phases.

Abstract

We carry out Monte Carlo simulations of the uniformly frustrated 3d XY model as a model for vortex line fluctuations in a high Tc superconductor. A density of vortex lines of f=1/25 is considered. We find two sharp phase transitions. The low T phase is an ordered vortex line lattice. The high T normal phase is a vortex line liquid with much entangling, cutting, and loop excitations. An intermediate phase is found which is characterized as a vortex line liquid of disentangled lines. In this phase, the system displays superconducting properties in the direction parallel to the magnetic field, but normal behavior in planes perpendicular to the magnetic field.