VOLTAGE NOISE DUE TO RANDOMLY INTERRUPTED MOTION OF VORTICES

The voltage noise generated by an randomly interrupted now of flux vortices across thin film superconducting strips is discussed. It is demonstrated that processes of vortex pinning and depinning, as well as motion of vortex-density fluctuations contribute to the noise spectra. Random switching of vortices between the state of pinning and now results in random telegraph noise-like behavior at high frequencies. The now of spatially non-correlated vortices, or vortex bundles, results in oscillatory peaks in the power spectra. The difference in frequency between two peaks is related to the inverse of the average time the vortices need to cross the sample. The shape of the voltage noise spectrum dramatically depends on the ratio of average lifetimes of vortices in the pinned and in the now state. Spectral oscillations are attenuated and disappear with increasing pinning strength. It is demonstrated that the physical picture depends on the type of geometrical resolution function chosen for the calculations.