Flux trapping in NbTiN strips

Abstract

We use scanning superconducting quantum interference device (SQUID) microscopy to image individual vortices in superconducting strips fabricated from NbTiN thin films. By repeatedly field-cooling strips of different widths in applied magnetic fields, we extract the threshold field at which the first vortex enters a strip, as well as the number and spatial configuration of vortices beyond this threshold. We model vortex behavior with and without considering the effect of pinning by numerically minimizing the Gibbs free energy of vortices in the strips. Our measurements provide a first experimental benchmark for understanding the flux trapping properties of NbTiN thin films, directly relevant to NbTiN-based superconducting circuits and devices.

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