Phase Transitions and Vortex Line Entanglement in a Model High Temperature Superconductor

TL;DR

This study uses Monte Carlo simulations of the 3d XY model to identify two phase transitions in high temperature superconductors, revealing vortex lattice melting and vortex entanglement phenomena.

Contribution

It introduces a detailed simulation-based analysis of vortex line phase transitions and entanglement in high temperature superconductors.

Findings

Vortex lattice melts at T_{cot} losing perpendicular coherence.

Vortex tangle percolates at T_{cz} destroying parallel coherence.

Cooling below T_{cz} results in a vortex entangled glassy state.

Abstract

Monte Carlo simulations of the uniformly frustrated 3d XY model are used to model vortex line fluctuations in high temperature superconductors in an applied magnetic field. We find two distinct phase transitions. At a lower T_{c\perp}, the vortex lattice melts and coherence is lost in planes perpendicular to the magnetic field. At a higher T_{cz}, a vortex tangle percolates throughout the system, and coherence is lost parallel to the magnetic field. Cooling below T_{cz}, high energy barriers for vortex line cutting lead to an entangled glassy state. Figures available upon request to stte@buckwheat.pas.rochester.edu.