Disorder-induced trapping and anti-trapping of vortices in type-II superconductors

TL;DR

This paper investigates how disorder affects vortex behavior in type-II superconductors, revealing a switch from vortex-defect attraction to repulsion with increasing magnetic field, supported by numerical simulations.

Contribution

It introduces a Ginzburg-Landau model with spatially varying diffusion to explain vortex-disorder interactions and demonstrates vortex switching phenomena through simulations.

Findings

Vortex-defect attraction switches to repulsion with magnetic field increase

Superconducting nuclei near suppressed diffusion regions can have nonzero vorticity

Numerical simulations show vortex arrangements in disordered superlattices

Abstract

We study the features of the superconductivity nucleation and vortex configurations in superconductors with modulated disorder. Using the Ginzburg-Landau-type theory with spatially varying diffusion coefficient, we uncover and explain the switching between the vortex-defect attraction to the repulsion upon the increase in the external magnetic field. It is shown that for rather weak applied magnetic fields, a superconducting nucleus localized near the region with the suppressed diffusion coefficient possesses a nonzero vorticity whereas the increase in the magnetic field can lead to a transition into the state with zero winding number. We demonstrate the manifestations of this switching phenomenon in superconductors with a large number of defects by performing numerical simulations of the vortex structures in superconductors with periodic spatial profiles of the diffusion coefficient. The obtained results clarify the physics of the vortex arrangement in several classes of the superconducting materials including one-dimensional superlattices and nanopatterned superconductors with regular arrays of the defects characterized by the increased concentration of nonmagnetic impurities.