Simple Vortex States in Films of Type-I Ginzburg-Landau Superconductor

TL;DR

This paper uses numerical Ginzburg-Landau calculations to explore vortex lattice structures in thin type-I superconductor films, revealing a stable square lattice phase and other configurations between the triangular lattice and intermediate state.

Contribution

It provides a detailed phase diagram of vortex lattice structures in thin type-I superconductor films, identifying a stable square lattice phase not previously characterized.

Findings

Stable square vortex lattice in certain thickness and field ranges

Triangular lattice stability in thinner films/lower fields

Rectangular lattices with varying aspect ratios

Abstract

Sufficiently thin films of type-I superconductor in a perpendicular magnetic field exhibit a triangular vortex lattice, while thick films develop an intermediate state. To elucidate what happens between these two regimes, precise numerical calculations have been made within Ginzburg-Landau theory at $\kappa=0.5$ and 0.25 for a variety of vortex lattice structures with one flux quantum per unit cell. The phase diagram in the space of mean induction and film thickness includes a narrow wedge in which a square lattice is stable, surrounded by the domain of stability of the triangular lattice at thinner films/lower fields and, on the other side, rectangular lattices with continuously varying aspect ratio. The vortex lattice has an anomalously small shear modulus within and close to the square lattice phase.