Regensburg 1998 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Postersitzung III: Spin-Peierls-Systeme, Metall-Isolator-Übergang, Lokalisierung; SL: Theorie; Quantenflüssigkeiten und -kristalle; Amorphe Materialien, Tunnelsysteme; Borcarbide, Fullerene, konventionelle SL; SL dünner Filme; Experimentiertechniken

TT 21.45: Poster

Donnerstag, 26. März 1998, 15:00–18:30, D

Spiral instability of the parallel current-field configuration in a thin superconducting film: a new model — •Yu.A. Genenko^1,2, P. Troche¹, J. Hoffmann¹, and H.C. Freyhardt¹ — ¹Institut f"ur Metallphysik, Universit"at G"ottingen, Windausweg 2, D-37073 G"ottingen — ²Donetsk Physical and Technical Institute, 340114 Donetsk, Ukraine

A phenomenon of regular voltage oscillations in a current-carrying superconductor in a parallel magnetic field was first observed experimentally in 1977 by Walmsley and Timms. It was in principle explained theoretically by Clem and Brandt who advanced theories of left-handed helical instability of a single flux-line and a flux-line lattice in the presence of a transport current. This theory gives so far the only reasonable explanation to the still weakly understood longitudinal resistivity of superconductors but the calculated dissipation rate is many orders less than that observed in the experiment. In this work we present a new model for the flux-line instability in a thin film. It is shown that the most easy way of this is the transformation of the initial linear vortex into a chain of 2D-vortices almost normal to the film surface and only slightly tilted in the field direction. The critical current of this chain instability is many orders less than that of the usual smooth-spiral process. The pitch length of the first instable spiral-like chain structure turns out to be of the order of the film thickness contrary to the infinite pitch length of the first helix that leads to the increasing of the dissipation rate by many orders.