Vortex motion noise in micrometer-sized thin films of the amorphous Nb0.7Ge0.3 weak-pinning superconductor - art. no. 014537

摘要

We report high-resolution measurements of voltage (V) noise in the mixed state of micrometer-sized thin films of amorphous Nb0.7Ge0.3, which is a good representative of weak-pinning superconductors. There is a remarkable difference between the noise below and above the irreversibility field B-irr. Below B-irr, in the presence of measurable pinning, the noise at small applied currents resembles shot noise, and in the regime of flux flow at larger currents decreases with increasing voltage due to a progressive ordering of the vortex motion. At magnetic fields B between B-irr and the upper critical field B-c2 flux flow is present already at vanishingly small currents. In this regime the noise scales with (1-B/B-c2)V-2(2) and has a frequency (f) spectrum of 1/f type. We interpret this noise in terms of the properties of strongly driven depinned vortex systems at high vortex density. [References: 27]