Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Postersession Superconductivity: Josephson Junctions, SQUIDs, Heterostructures, Andreev Scattering, Vortex Physics, Cryodetectors, Measuring Devices, Cryotechnique
TT 32.4: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Thermal and Quantum Escape of Fractional Josephson Vortices — •Hanna Pöhler1, Uta Kienzle1, Kai Buckenmaier1, Tobias Gaber1, Michael Siegel2, Dieter Koelle1, Reinhold Kleiner1, and Edward Goldobin1 — 1Physikalisches Institut, Center for Collective Quantum Phenomena, Universität Tübingen, Germany — 2Institut für Mikro- und Nanoelektronische Systeme, Universität Karlsruhe (KIT), Germany
By using a pair of tiny current injectors one can create an arbitrary κ discontinuity of the phase in a long Josephson junction (LJJ) and a fractional Josephson vortex (FJV), carrying a fraction Φ /Φ0=κ/2π≤1 of the magnetic flux quantum Φ0≈ 2.07 · 10−15 Wb, which is pinned at the discontinuity [1]. If a bias current I, exceeds the critical value Ic(κ) [2,3], an integer fluxon is torn off the discontinuity and the LJJ switches to the voltage state. Due to thermal or quantum fluctuations this escape event may occur at I Ic(κ).[4]
We have measured the critical current distribution P(I) for different values of κ, temperature T and junction geometry. At low temperatures we see a saturation of the distribution width which is presumably due to the crossover from thermal activation to quantum tunnelling. The results are compared to numerical simulations based on the static sine-Gordon equation.
[1] E. Goldobin, et al., Phys. Rev. B 70, 174519 (2004).
[2] A. V. Ustinov, Appl. Phys. Lett. 80, 3153 (2002).
[3] B. A. Malomed and A. V. Ustinov, Phys. Rev. B 69, 64502 (2004).
[4] P. Hänggi, et al., Rev. Mod. Phys. 62, 251 (1990)