Second generation of vortex-antivortex states in mesoscopic superconductors: stabilization by artificial pinning

TL;DR

This paper demonstrates that artificial pinning arrays in mesoscopic superconductors can stabilize vortex-antivortex states deep within the superconducting phase, overcoming their usual fragility and enabling experimental observation.

Contribution

It introduces a novel method of stabilizing vortex-antivortex states using artificial pinning, independent of sample symmetry, in large mesoscopic superconductors.

Findings

Vortex-antivortex states can be stabilized by artificial pinning arrays.

Pinning prevents vortex-antivortex annihilation even in large samples.

Stable V-Av molecules can exist deep in the superconducting state.

Abstract

Antagonistic symmetries of superconducting polygons and their induced multi-vortex states in a homogeneous magnetic field may lead to appearance of antivortices in the vicinity of the superconducting/normal state boundary (where mesoscopic confinement is particularly strong). Resulting vortex-antivortex (V-Av) molecules match the sample symmetry, but are extremely sensitive to defects and fluctuations and remain undetected experimentally. Here we show that V-Av states can re-appear deep in the superconducting state due to an array of perforations in a polygonal setting, surrounding a central hole. Such states are no longer caused by the symmetry of the sample but rather by pinning itself, which prevents the vortex-antivortex annihilation. As a result, even micron-size, clearly spaced V-Av molecules can be stabilized in large mesoscopic samples.