Vortex ratchet effect in superconductor open nanotubes and nanopetals

Abstract

Advancements in the fabrication of superconducting 3D nanostructures and the creation of artificial pinning sites pave the way to novel applications and enhancement of nanosensors, bolometers, and quantum interferometers. The dynamics of magnetic flux quanta (Abrikosov vortices) in 3D nanoarchitectures reveal a rich palette of phenomena unseen in planar counterparts. Here, we consider two types of superconductor 3D nanostructures -- open nanotubes and nanopetals -- carrying an azimuthal transport current in a homogeneous external magnetic field. The complex 3D geometry of the structures induces an inhomogeneity of the normal magnetic field and makes the vortices move along preferred paths. By introducing a series of asymmetric pinning sites along these paths, we demonstrate non-reciprocity in the flux transport, which, in the 3D nanostructures, is stronger than in the planar membranes. The enhancement of the vortex ratchet effect manifests via a difference in the vortex depinning current under current reversal in a wider range of magnetic fields. The revealed effect is attributed to the inhomogeneous field-induced vortex channeling through the areas containing the asymmetric pinning sites. Our results demonstrate that the ratchet effect can persist up to higher magnetic fields via extending a superconducting film into the third dimension, without an increase in the number of asymmetric pinning sites.