Dynamic evolution of flux distributions in a pulse-driven superconductor by high-speed magneto-optical imaging

Abstract

The accurate understanding of flux dynamics is essential for the design and operation of superconducting circuits. Time evolution of flux-density distribution in an NbN strip by the transport current was observed using high-speed magneto-optical microscopy. It was determined that even for the dynamic penetration and exclusion of vortices under the transport current, the surface barrier is essential. This feature is important for the correct understanding of the complex behavior of state-of-the-art superconducting devices.

Critical current in thin flat superconductors with Bean-Livingston and geometrical barriers

“…However, formula (41) has been derived, considering a single vortex. Since the vortex domes on the lateral surface of the strip modify the current distribution in the sample, the H p has to be calculated self-consistently.…”

“…In this case one has i H ≈ I/πwH a → ∞, and the vortex dome is absent in the sample. Then, the vortex-entry conditions ( 29) and (41) give the following expressions for I c (0) in the cases of the Bean-Livingston and geometrical barriers, respectively:…”