Rising Speed Limits for Fluxons via Edge-Quality Improvement in Wide MoSi Thin Films

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