&ball; Physics 15, s77
Researchers have identified and studied vortex jets – swirling streams of electrons – that can form at edge defects in current-carrying superconductors.
A material defect at the edge of a superconductor can act as a gate for the entry of vortices – small loops of electrical current. But what trajectories do these vortices take inside the superconductor? And how do these paths change if the current in the material is increased or an external magnetic field is added? Oleksandr Dobrovolskiy of the University of Vienna and his colleagues have now answered these questions . The findings could lead to the observation of new effects in superconductors, such as the generation of sound and spin waves.
In theoretical work, researchers have found that vortices created at an edge defect on a superconducting strip form a jet that passes through the strip thanks to the Lorentz force. This jet is narrow near the fault, but the mutual repulsion between the vortices causes it to widen as it moves to the opposite edge of the band. Such broadening produces a local voltage perpendicular to the current in the material, and this voltage first increases and then decreases as the current increases. The team derived expressions for the jet shape in narrow and wide bands and, for the latter, determined how this shape is affected by an external magnetic field.
In experiments, Dobrovolskiy and his colleagues confirmed their predicted voltage-current relationship for narrow bands. For broad bands, they showed that the derived magnetic field dependence of the jet shape is in agreement with previous observations. Finally, the researchers corroborated their findings with simulations, which showed that the jet narrows and then forms a “river” as the current increases. Adding to the researchers’ understanding of vortex dynamics in superconductors, the results could improve the performance of single-photon detectors based on superconductors.
Ryan Wilkinson is a freelance science editor and writer based in Durham, UK.
- AI Bezuglyj et al.“Vortex jets generated by edge defects in current-carrying superconducting thin strips”, Phys. Rev. B 105214507 (2022).