Rising speed limits for fluxons via edge quality improvement in wide MoSi thin films

• Published in: arXiv.org
• Main Authors: Budinska, B, Aichner, B, D Yu Vodolazov, M Yu Mikhailov, Porrati, F, Huth, M, Chumak, A V, Lang, W, Dobrovolskiy, O V
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 26.11.2021
• Subjects: Deduction; Dynamic stability; Elementary excitations; Flow stability; Fluid flow; Ion beams; Laser etching; Magnetic flux; Photons; Physics - Materials Science; Physics - Superconductivity; Speed limits; Superconductors; Thin films
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2111.13431

Ultra-fast vortex motion has recently become a subject of extensive investigations, triggered by the fundamental question regarding the ultimate speed limits for magnetic flux quanta and enhancements of single-photon detectors. In this regard, the current-biased quench of a dynamic flux-flow regime - flux-flow instability (FFI) - has turned into a widely used method for the extraction of information about the relaxation of quasiparticles (unpaired electrons) in the superconductor. However, the large relaxation times \(\tau_\epsilon\) deduced from FFI for many superconductors are often inconsistent with the fast relaxation processes implied by their single-photon counting capability. Here, we investigate FFI in \(15\) nm-thick \(182\) \(\mu\)m-wide MoSi strips with rough and smooth edges produced by laser etching and milling by a focused ion beam. For the strip with smooth edges we deduce, from the current-voltage (\(I\)-\(V\)) curve measurements, a factor of 3 larger critical currents \(I_\mathrm{c}\), a factor of 20 higher maximal vortex velocities of 20 km/s, and a factor of 40 shorter \(\tau_\epsilon\). We argue that for the deduction of the intrinsic \(\tau_\epsilon\) of the material from the \(I\)-\(V\) curves, utmost care should be taken regarding the edge and sample quality and such a deduction is justified only if the field dependence of \(I_\mathrm{c}\) points to the dominating edge pinning of vortices.