Abrikosov fluxonics [1], a domain of science and engineering at the interface between superconductivity research and nanotechnology, is concerned with the study of properties and dynamics of Abrikosov vortices in nanoengineered superconductors, with particular focus on their confinement, manipulation, and exploitation for emerging functionalities. In this regard, of special interest are the ultimate speed limits for magnetic flux transport via fluxons as well as the quasiparticle relaxation mechanisms underlying these limits and determining the suitability of superconductors for single-photon detectors and magnons generators of the Cherenkov type [2].
In my talk, I will address the issue of vortex velocity enhancement in the context of these two applications. First, nanoengineered superconductors with weak volume pinning and close-to-depairing criticial currents will be introduced as materials supporting vortex velocities exceeding 10 km/s [3]. Herewith, high quality of the edge of the superconducting strip is decisive for the suppression of the flux-flow instability [4]. Next, single edge defects will be presented as tools for the formation of vortex jets [5] and the deduction of the number of vortices and their velocity [6]. Finally, in superconductor-ferromagnet hybrid structures, fast motion of a vortex lattice allows for the emission of spin waves (magnons) via a Cherenkov-type mechanism and the formation of unidirectional spin-wave beams [7]. The emission of spin waves is accompanied by a magnon Shapiro step in the superconductor's current-voltage curve because of the phase-locking of the spin waves with the moving vortex lattice and reduces the dissipation in the superconductor.
[1] Abrikosov fluxonics in washboard nanolandscapes, O. Dobrovolskiy, Physica C 533, 80–90 (2017)
[2] Cherenkov radiation of spin waves by ultra-fast moving magnetic flux quanta, O. Dobrovolskiy et al. arXiv:2103.10156.
[3] Ultra-fast vortex motion in a direct-write Nb-C superconductor, O. Dobrovolskiy et al. Nat. Commun. 11, 3291, (2020).
[4] Rising speed limits for fluxons via edge quality improvement in wide MoSi thin films, B. Budinska et al., Phys. Rev. Appl. 17, 034072 (2022).
[5] Vortex jets generated by edge defects in current-carrying superconductor thin strips, A. Bezuglyj et al., Phys. Rev. B 105, 214507 (2022).
[6] Vortex counting and velocimetry for slitted superconducting thin strips, V. M. Bevz et al. Phys. Rev. Appl. 19, 034098 (2023).