Uniformly frustrated XY model: strengthening of the vortex lattice by intrinsic disorder

TL;DR

This study uses Monte Carlo simulations to show that intrinsic disorder in superconducting films can strengthen the vortex lattice and increase the critical temperature under magnetic fields, contrary to typical effects.

Contribution

It demonstrates how intrinsic disorder can enhance the vortex lattice stability and critical temperature in the uniformly frustrated XY model under magnetic fields.

Findings

Superconducting critical temperature $T_c$ increases with magnetic field $H$ for weak pinning.

Strong pinning restores the decreasing $T_c$-$H$ dependence seen in experiments.

Disorder can reinforce the vortex lattice against thermal fluctuations.

Abstract

In superconducting films, the role of intrinsic disorder is typically to compete with superconductivity by fragmenting the global phase coherence and lowering the superfluid density. Nonetheless, when a transverse magnetic field is applied to the system and an Abrikosov vortex lattice forms, the presence of disorder can actually strengthen the superconducting state against thermal fluctuations. By means of Monte Carlo simulations on the uniformly frustrated XY model in two dimensions, we show that while for weak pinning the superconducting critical temperature $T_c$ increases with the applied field $H$, for strong enough pinning the experimental decreasing dependence between $T_c$ and $H$ is recovered with a resulting more robust vortex lattice.