Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 31: SC: Tunnelling, Josephson Junctions
TT 31.6: Vortrag
Donnerstag, 25. März 2010, 10:45–11:00, H21
Optimization of Nb/Al-AlOx/Nb Technology for the Investigation of Fluxon Dynamics in Long Josephson Junctions — •Johannes M. Meckbach1, Christoph Kaiser1, Konstantin Il’in1, Michael Siegel1, Kai Buckenmaier2, Tobias Gaber2, Uta Kienzle2, Hanna Sickinger2, Edward Goldobin2, Reinhold Kleiner2, and Dieter Koelle2 — 1Institut für Mikro- und Nanoelektronische Systeme, KIT, Germany — 2Physikalisches Institut - Experimentalphysik II, Universität Tübingen, Germany
Underdamped long Josephson junctions (LJJs) are ideal systems for the investigation of fluxon dynamics. In LJJs the Josephson phase may vary on the length scale of λJ, the Josephson penetration depth, and thus is very sensitive to defects in the structure. Inhomogeneities in the barrier can lead to a locally suppressed critical current density and parasitic resonances in the microwave spectra of the JJ. We have developed and optimized the process for Nb/Al-AlOx/Nb based LJJs exhibiting an exceptionally high quality. We show spectroscopic measurements which confirm the uniformity of the AlOx barriers.
In very long linear JJs, the bias current peaks at the edges while the central part of LJJs is left almost unbiased. This results in unusual Ic(H) dependences with reduced Ic(0) and hampers the control of (semi)fluxons situated near the center of LJJs. To optimize the bias feed circuitry, we have investigated a variety of bias line geometries (multiple lines, resistors, etc.) measuring the scaling of the maximum critical current over the JJ length. We discuss advantages and drawbacks of these designs.