Current-assisted thermally activated flux liberation in ultrathin nanopatterned NbN superconducting meander structures

We present results from an extensive study of fluctuation phenomena in superconducting nanowires made from sputtered NbN. Nanoscale wires were fabricated in form of a meander and operated at a constant temperature T≈0.4Tc(0). The superconducting state is driven close to the electronic phase transition by a high bias current near the critical one. Fluctuations of sufficient strength temporarily drive a section of the meander structure into the normal-conducting state, which can be registered as a voltage pulse of nanosecond duration. We considered three different models (vortex-antivortex pairs, vortex edge barriers, and phase-slip centers) to explain the experimental data. Only thermally excited vortices, either via unbinding of vortex-antivortex pairs or vortices overcoming the edge barrier, lead to a satisfactory and consistent description for all measurements. CURRENT ASSISTED, THERMALLY ACTIVATED FLUX LIBERATION IN ULTRATHIN NANOPATTERNED NbN SUPERCONDUCTING MEANDER STRUCTURES H. Bartolf, A. Engel, A. Schilling Physics-Institute, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland K. Il’in, M. Siegel Institute of Micround Nano-electronic Systems, University of Karlsruhe, Hertzstrasse 16, D-76187 Karlsruhe, Germany H.-W. Hübers and A. Semenov DLR Institute of Planetary Research, Rutherfordstrasse 2, 12489 Berlin, Germany