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TT: Fachverband Tiefe Temperaturen

TT 10: Superconductivity: Tunneling, Josephson Junctions, SQUIDs

TT 10.6: Talk

Monday, March 23, 2009, 15:30–15:45, HSZ 105

Visualizing supercurrents in 0-π ferromagnetic Josephson tunnel junctions — •Edward Goldobin¹, Christian Gürlich¹, Tobias Gaber¹, Dieter Koelle¹, Reinhold Kleiner¹, Martin Weides², and Hermann Kohlstedt² — ¹Physikalisches Institut and Center for Collective Quantum Phenomena, Universität Tübingen, Germany — ²Institute of Solid State Physics, Reserch Center Jülich, Germany

So-called 0 and π Josephson junctions can be treated as having positive and negative critical currents. This implies that the same phase shift applied to a Josephson junction causes counterflow of supercurrents in 0 and in π junctions connected in parallel provided they are short in comparison with Josephson penetration depth λ_J.

We have fabricated several 0, π, 0-π, 0-π-0 and 20×(0-π-) planar superconductor-insulator-ferromagnet-superconductor Josephson junctions and studied the spatial supercurrent density distribution j_s(x,y) across the junction area using low temperature scanning electron microscopy. At zero magnetic field we clearly see counterflow of the supercurrents in 0 and π regions. The picture also changes consistently in the applied magnetic field.