Intrinsic 1/f noise in a superconductor strip

A widely used configuration in superconductivity-based electronics is a thin superconductor strip in the presence of a normally incident magnetic field. For a weak magnetic field, close to the vortex-penetration threshold field, the vortex-penetration potential consists of a moderate ridge near the mid-strip line and two minima along the strip edges. The low-frequency electric-field noise generated by thermally activated vortex hops between these two minima is derived for the case where the minima extensions substantially exceed that of the vortex core. The ensuing noise shape spectrum is approximately '1/.f' for a 'wide' strip, and a plateau followed by a drop at higher frequencies for a 'narrow' strip. Corresponding flux noise is estimated in two instances. Since this noise is a consequence of the strip geometry and not depending on material defects, it is predicted to be omnipresent and its magnitude constitutes a lower noise-level limit. Published by Elsevier Science B.V.