Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 46: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs 2
TT 46.8: Talk
Thursday, March 29, 2012, 19:45–20:00, H 2053
Versatile Multi-Layer Josephson Junction Process for Vortex Molecules — •Johannes Maximilian Meckbach1, Simon Bühler1, Michael Merker1, Konstantin Il’in1, Michael Siegel1, Kai Buckenmaier2, Tobias Gaber2, Uta Kienzle2, Benjamin Neumaier2, Edward Goldobin2, Reinhold Kleiner2, and Dieter Koelle2 — 1Institut für Mikro- und Nanoelektronische Systeme, KIT, Germany — 2Physikalisches Institut - Experimentalphysik II, Universität Tübingen, Germany
In long Josephson junctions magnetic flux may penetrate the barrier resulting in a so-called Josephson-Vortex carrying one flux quantum Φ0. In recent years a new type of Josephson-Vortex became available, which carries any arbitrary fraction Φ = −Φ0 κ / 2π of magnetic flux. These fractional vortices (℘-vortices) spontaneously appear at discontinuities of the Josephson phase along the junction, which in turn are created using a pair of current injectors.
We present a new Nb/Al-AlOx/Nb process for the fabrication of Josephson junctions of very high quality. Placing two injector pairs along the strongly underdamped long junctions allows the investigation of fractional vortex molecules. The topological charge of each vortex and their interaction can be altered even during experiment by changing the individual injector currents. Vortex molecule states have been measured using asymmetric DC-SQUIDs coupled to the vortices by overlying pick-up loops. To uphold the ℘-vortices we use persistent currents, which can be altered using heat switches. Fractional vortex molecules are promising candidates for a new type of qubits.