Phase Transitions in Mesoscopic Superconducting Films

TL;DR

This paper investigates phase transitions in mesoscopic square superconducting films by solving the Ginzburg-Landau equation, revealing the existence of antivortex phases and topological transitions influenced by the Ginzburg-Landau parameter.

Contribution

It provides a detailed analysis of vortex and antivortex states in mesoscopic superconducting films across a wide range of parameters, including the stability of giant vortices.

Findings

Antivortex phases exist over a broad parameter range.

Topological phase transitions occur with decreasing coherence length.

Giant vortex with vorticity 3 is unstable for all examined conditions.

Abstract

We solve the Ginzburg-Landau equation (GLE) for the mesoscopic superconducting thin film of the square shape in the magnetic field for the wide range of the Ginzburg-Landau parameter $0.05<\kappa_{eff}<\infty $. We found that the phase with the antivortex exists in the broad range of parameters. When the coherence length decreases the topological phase transition to the phase with the same total vorticity and a reduced symmetry takes place. The giant vortex with the vorticity $m=3$ is found to be unstable for any field, $\xi /a$ and $\kappa_{eff}\ge 0.1$. Reduction of $ \kappa _{eff}$ does not make the phase with antivortex more stable contrary to the case of the cylindric sample of the type I superconductor.