Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 66: Superconductivity: Tunneling, Josephson Junctions, SQUIDs

TT 66.7: Vortrag

Mittwoch, 18. März 2015, 16:30–16:45, H 2053

Experiments on phase retrapping in ϕ Josephson junctions — •Edward Goldobin¹, Rosina Menditto¹, Martin Weides², Dieter Koelle¹, and Reinhold Kleiner¹ — ¹University of Tübingen, Tübingen, Germany — ²KIT, Karlsruhe, Germany

We experimentally study retrapping of the phase in ϕ Josephson junctions (JJs) based on superconductor-insulator-ferromagnet-superconductor (SIFS) 0-π heterostructures[1,2]. Such ϕ JJs have a doubly degenerate ground state (two potential energy wells) with the phases ±ϕ (0<ϕ<π). We study in which of these two wells the phase is trapped upon return of the JJ to the zero voltage state. We find that for T>T^*≈2.4 K (large damping) the phase is always trapped in the +ϕ state. However, for lower T (small damping) the trapping result is a statistical mixture of the +ϕ and the −ϕ states due to the presence of noise in the system. The probability for retrapping to the −ϕ state increases and oscillates as T is decreasing below T^*, reaching a saturation value of ∼ 30% for T1.2 K. These results are compared with theory[3], which predicts the butterfly effect in the limit of low damping.

[1] E. Goldobin et al. Phys. Rev. Lett. 107, 227001 (2011).

[2] H. Sickinger et al. Phys. Rev. Lett. 109, 107002 (2012).

[3] E. Goldobin et al. Phys. Rev. Lett. 111, 057004 (2013).