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

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 ${\tau }_{\epsilon }$ 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.

10 pages, 5 figures

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Cited by in corpus (8)

• Vortex jets generated by edge defects in current-carrying superconductor thin strips
• Vortex counting and velocimetry for slitted superconducting thin strips
• Impact of border defects on the magnetic flux penetration in superconducting films
• Fast Dynamics of Vortices in Superconductors
• Evolution of dissipative regimes in atomically thin ${\text{Bi}}_2{\text{Sr}}_2{\text{CaCu}}_2{\text{O}}_{8+x}$ superconductor
• Picosecond Trajectory of Two-dimensional Vortex Motion in FeSe${}_{0.5}$Te${}_{0.5}$ Visualized by Terahertz Second Harmonic Generation
• DC-driven separation of fractional flux quanta in two-band superconductors
• Vortex rivers and multiple voltage transitions in superconducting MgB${}_2$ thin films