Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 11: Superconductivity: Tunneling, Josephson Junctions, SQUIDs

TT 11.3: Talk

Monday, February 25, 2008, 16:00–16:15, H 3010

Magnetic flux dynamics in 0, π and 0-π SIFS Josephson junctions — •Judith Pfeiffer¹, Martin Weides², Matthias Kemmler¹, Alexey K. Feofanov³, Jürgen Lisenfeld³, Dieter Koelle¹, Alexey V. Ustinov³, Reinhold Kleiner¹, and Edward Goldobin¹ — ¹Physikalisches Institut-Experimentalphysik II and Center for Collective Quantum Phenomena, Universität Tübingen, D-72076 Tübingen, Germany — ²Center of Nanoelectronic Systems for Information Technology (CNI), Research Centre Jülich, D-52425 Jülich, Germany — ³Physikalisches Institut III, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany

We present experimental and numerical studies of high quality underdamped Superconductor-Insulator-Ferromagnet-Superconductor (SIFS) Josephson junctions fabricated as Nb/Al₂O₃/Cu₄₀Ni₆₀/Nb heterostructures. Varying the thickness of the ferromagnetic barrier one can fabricate 0, π and 0-π junctions. The dynamic and static properties of these junctions are studied by measuring the I-V characteristic and critical current I_c vs. magnetic field H. Using microwave spectroscopy we have investigated the eigenfrequencies of a 0, π and 0-π Josephson junction in the temperature range 4.2 K...300 mK. Harmonic, subharmonic and superharmonic pumping is observed in experiment and the experimental data are compared with numerical simulations. Perfoming thermal escape measurements at temperatures down to 300 mK we try to reach the quantum tunnelling regime.