Vortex-Line Phase Diagram for Anisotropic Superconductors

TL;DR

This paper maps the vortex-line phase diagram in anisotropic superconductors like BSCCO and YBCO, revealing three distinct phases and providing detailed insights near the lower critical field.

Contribution

It introduces a numerical method using simulated annealing to accurately determine the vortex phase diagram in anisotropic superconductors.

Findings

Identifies three distinct vortex phases in the phase diagram.

Provides detailed characterization of phases near the lower critical field.

Uses an exact Gibbs free energy minimization in the London approximation.

Abstract

The zero temperature vortex phase diagram for uniaxial anisotropic superconductors placed in an external magnetic field tilted with respect to the axis of anisotropy is studied for parameters typical of BSCCO and YBCO. The exact Gibbs free energy in the London approximation, using a self-energy expression with an anisotropic core cutoff, is minimized numerically, assuming only that the equilibrium vortex state is a vortex-line-lattice with a single vortex line per primitive unit cell. The numerical method is based on simulated annealing and uses a fast convergent series to calculate the energy of interaction between vortex lines. A phase diagram with three distinct phases is reported and the phases are characterized in detail. New results for values of the applied field close to the lower critical field are reported.