Influence of Thermal Fluctuations on Uniform and Nonuniform Superconducting Rings according to the Ginzburg-Landau and the Kramer-Watts-Tobin Models - Condensed Matter > SuperconductivityReport as inadecuate




Influence of Thermal Fluctuations on Uniform and Nonuniform Superconducting Rings according to the Ginzburg-Landau and the Kramer-Watts-Tobin Models - Condensed Matter > Superconductivity - Download this document for free, or read online. Document in PDF available to download.

Abstract: We evaluate the influence of thermal fluctuations on superconducting ringsthat enclose a magnetic flux, using the time-dependent Ginzburg-Landau TDGLor the Kramer-Watts-Tobin KWT model, while thermal fluctuations areaccounted for by means of Langevin terms. This method is applicable insituations where previous methods are not, such as nonuniform loops, rings withlarge width to radius ratio and loops with large coherence length to perimeterratio. We evaluate persistent currents, position and statistical behavior offlux-induced vortices and lifetime of metastable fluxoid states. The influenceof nonuniformity on the persistent current does not depend strongly on thedetails of the cross-section profile; it depends mainly on its first harmonic,but not only on it. As a consequence of nonuniformity the maximum of thepersistent current shifts to smaller fluxes and the passage between fluxoidstates remains non-hysteretic down to lower temperatures than in the case of auniform sample. Our results using TDGL agree remarkably well with recentmeasurements of the persistent current in superconducting rings and withmeasurements of the position of a vortex that mediates between fluxoid statesin an asymmetric disk with a hole; they could also provide a plausibleexplanation for unexpectedly short measured lifetimes of metastable states.Comparison between TDGL and KWT indicates that they lead to the same resultsfor the persistent current, whereas KWT leads to larger lifetimes than TDGL.



Author: Jorge Berger

Source: https://arxiv.org/







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