Symmetric and non-symmetric vortex-antivortex molecules in fourfold superconducting geometry

TL;DR

This paper demonstrates how artificial fourfold pinning can induce and enhance the observation of symmetric and asymmetric vortex-antivortex molecules in superconducting squares, revealing new stable states and nucleation pathways.

Contribution

It introduces a method to enforce and detect vortex-antivortex states in superconductors using artificial pinning, expanding understanding of vortex dynamics.

Findings

Artificial fourfold pinning enhances vortex-antivortex states

Stable asymmetric vortex-antivortex equilibria exist

Vortex-antivortex nucleation can be driven by temperature or magnetic field

Abstract

In submicron superconducting squares in a homogeneous magnetic field, Ginzburg-Landau theory may admit solutions of the vortex-antivortex type, conforming with the symmetry of the sample [Chibotaru et al., Nature 408, 833 (2000)]. Here we show that these fascinating, but never experimentally observed states, can be enforced by artificial fourfold pinning, with their diagnostic features enhanced by orders of magnitude. The second-order nucleation of vortex-antivortex molecules can be driven either by temperature or applied magnetic field, with stable asymmetric vortex-antivortex equilibria found on its path.