Fluxon manipulation by nanoscale artificial pinning lattices in cuprate superconductors

Superconductivity is an exciting phenomenon that raises many unexplored fundamental questions and has enormous relevance for emerging and disruptive technologies. Apart from the well-known applications of almost loss-less energy transport in superconducting cables and the creation of intense magnetic fields by superconducting coils, recent advances in the nanostructuring of superconductors make them promising candidates for novel quantum technologies.

Inside a superconductor, a magnetic field can exist only in small quantized units, called fluxons or vortices. In a homogeneous and pure superconductor, the fluxons are arranged in a hexagonal lattice. It is by the introduction of controlled defects that the properties of superconductors can be tailored to allow for a control of these fluxons, for instance by forcing them into a predefined formation by traps.

While the brittle nature and the complicated crystal structure of the copper-oxide high-temperature superconductors pose a challenge to their technical usability, this project will turn this susceptibility into an asset to fabricate superconducting nanostructures with unprecedented resolution. Point defects are created by helium ion irradiation with moderate energy that readily suppress superconductivity locally. These individual small regions of non-superconducting material act as the traps for the fluxons and they all together form a pinning landscape in the superconductor. Using shadow projection of a wide-field ion beam through a stencil mask or the focused beam of a helium-ion microscope, it is possible to pattern nanoscale pinning landscapes into copper-oxide superconductors with unprecedented small distances. This leads to a much stronger interaction of the fluxons than it could be achieved in previous experiments and opens the door to investigate many novel phenomena.
The scientific results of this project may have significant implications on the understanding of vortex physics, on the development of new functional materials, on the development of ultrafast low-dissipation superconducting circuits, and may lead to improvements of very small magnetic field sensors (SQUIDs) based on copper-oxide superconductors.

This research program will be performed in tight collaboration of three expert groups at the University of Vienna, the Johannes Kepler University of Linz, and the Eberhard Karls University in Tübingen. Theoretical support with molecular-dynamic simulations will be provided by collaborators at the University of Antwerp and the visualization of the fluxon patterns will be performed at the Universidad Autónoma de Madrid.