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SYQI: Quantum information processing in condensed media
SYQI 3: Poster
SYQI 3.4: Poster
Wednesday, March 26, 2003, 14:30–19:00, P2d
Josephson phase escape in long Josephson junctions by quantum nucleation of vortex-antivortex pairs — •M. V. Fistul, A. Wallraff, Yu. Koval, J. Lisenfeld, A. Lukashenko, and A. V. Ustinov — Physikalisches Institut III, Universität Erlangen-Nürnberg, Erlangen
We present a theoretical and experimental study of a switching from the superconducting state to the resistive state in long narrow annular Josephson junctions. In the presence of a magnetic field H parallel to the junction plane we obtain an increase of the width of switching current distribution P(Ic). We attribute this increase to the crossover from the Josephson phase escape in a whole Josephson junction to the fluctuation induced vortex-antivortex pair nucleation. Such a nucleation process is described by Josephson phase escape in the effective potential created by external magnetic field and dc bias. We predict a peculiar magnetic field dependence of the macroscopic energy levels, and at low temperatures the crossover to the macroscopic quantum nucleation of the vortex-antivortex pair. Our theoretical analysis is in a good agreement with experimental results that show the crossover to a quantum regime at the temperature of about 100 mK.