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arXiv · 2111.13431

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

B. Budinska·B. Aichner·D. Yu. Vodolazov·M. Yu. Mikhailov·F. Porrati·M. Huth·A. V. Chumak·W. Lang·O. V. Dobrovolskiy
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Abstract

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 $τ_ε$ 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 $182$ $μ$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 $τ_ε$. We argue that for the deduction of the intrinsic $τ_ε$ 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.

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B. Budinska, B. Aichner, D. Yu. Vodolazov, M. Yu. Mikhailov, F. Porrati, M. Huth, A. V. Chumak, W. Lang, O. V. Dobrovolskiy. 2021-11-26. Rising speed limits for fluxons via edge quality improvement in wide MoSi thin films. https://doi.org/10.1103/physrevapplied.17.034072

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