Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 10: Superconductivity - Tunneling, Josephson Junctions, SQUIDs

TT 10.3: Talk

Saturday, March 5, 2005, 09:00–09:15, TU H104

Thermally induced injection of vortices in narrow long Josephson junctions — •Abdufarrukh A. Abdumalikov¹, Mikhail V. Fistul², and Alexey. V. Ustinov¹ — ¹Physikalisches Institut III, Universität Erlangen-Nürnberg, D-91058 Erlangen — ²Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum

We report an experimental and theoretical study of a novel resistive state in ultra-narrow long Josephson junctions induced by thermal fluctuations. In the presence of an externally applied magnetic field, the hysteretic current-voltage characteristics show a low-voltage branch emerging directly from the superconducting state. We explain this feature by random injection of vortices into the junction in the presence of a large high-frequency damping. We obtain the current-voltage characteristics by calculating the dc bias dependent activation rate of the vortex injection. This activation rate is determined by a surface barrier that is controlled by an external magnetic field. Our theoretical analysis, taking into account thermally induced injection of vortices, quantitatively agrees with experimental results.