In a recent work, a collaboration of researchers from IFIMAC at Madrid, with researchers from Valencia and Hamburg makes for the first time a combined study of magnetic impurities and vortices in superconductors, surfacing new behavior that might be used to improve quantum computation. Researchers showed that magnetic impurities mix different quantum levels inside vortices. Different quantum levels host states with different spatial density distributions. The mixture thus produces a spatial shift in the quantum levels of vortex cores at the location of the impurity. The crux is that the spatial shift survives, even when the difference between quantum levels is too tiny to be measured. To show such effects in an experiment, researchers made detailed calculations and found that Fe ions produce a sizeable magnetic moment, strong enough to disturb superconductivity in layered 2H-NbSe2.
They then studied these Fe atoms using a powerful microscope, called scanning tunneling microscope and characterized their mixed electron hole character and some of their magnetic properties. Finally, they applied a magnetic field and visualized vortices surrounded by Fe impurities. As expected by their calculations, they saw that vortices are electron hole asymmetric, whereas they remained electron hole symmetric in absence of magnetic impurities. The combined effort of calculations and experiment brings the subject a step forward by showing that a quantum property, the asymmetric electron hole character, which is absent in vortices, can be transferred to vortices by locating these close to magnetic impurities. [Full article]