You are here

    • You are here:
    • Home > STP497 - Escape and Retrapping Experiments with Josephson ϕ Junctions

STP497 - Escape and Retrapping Experiments with Josephson ϕ Junctions

Escape and Retrapping Experiments with Josephson φ Junctions

E. Goldobin1, R. Menditto1, H. Sickinger1, M. Weides2, H. Kohlstedt3, J.M. Meckbach4, M. Merker4, K. Ilin4, M. Siegel4, D. Koelle1, R. Kleiner1
1Physikalisches Institut and Center for Collective Quantum Phenomena in LISA+, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen, Germany
2Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
3Technische Fakultät, Institut für Elektrotechnik und Informationstechnik, Nanoelektronik, Universität zu Kiel, Kaiserstr. 2, 24143 Kiel, German
4Institut für Mikro- und Nanoelektronische Systeme, Universität Karlsruhe (TH), Hertzstrasse 16, 76187 Karlsruhe, Germany
Abstract — A φ Josephson junction (JJ) is a junction having a degenerate ground state phase ±ϕ (0 < φ < π) [1]. This results from a specific Josephson energy profile, which looks like a 2π-periodic double-well potential. Such φ JJs have unusual physical properties and attractive for applications such as phase batteries for classical and quantum digital circuits, memory or random number generators [2-9].
In my talk I will revisit the key properties of ϕ JJs that can be seen experimentally, e.g., two critical currents that can be used for detecting the internal state of the ϕ JJ [6]. Further I will present our recent experiments on phase escape and retrapping in different types of ϕ JJs.
By measuring the switching current histograms that, in general, exhibit two escape peaks corresponding to critical currents Ic+, we are able to calculate the probability of the phase to be trapped in -ϕ and +ϕ wells when the junction returns from non-zero- to zero-voltage-state. We show that, similar to the theoretical prediction [4], at high temperature the retrapping is deterministic (always in the +ϕ well), while at lower temperature we observe an onset of the butterfly effect with an oscillating probability of trapping in a particular well. Unexpectedly, the probability of trapping in a particular well saturates at a value different than 50% at low temperatures
[1] E. Goldobin et al., Phys. Rev. Lett. 107, 227001 (2011)
[2] R. G. Mints et al., Phys. Rev. B 57, R3221 (1998)
[3] A. Buzdin et al., Phys. Rev. B 67, 220504(R) (2003)
[4] E. Goldobin, et al. Phys. Rev. Lett. 111, 057004 (2013)
[5] A. Lipman et al., Phys. Rev. B 90, 184502 (2014)
[6] H. Sickinger et al., Phys. Rev. Lett. 109, 107002 (2012)
[7] E. Goldobin et al., Appl. Phys. Lett. 102, 242602 (2013)
[8] E. Goldobin et al., Phys. Rev. B 91, 214511 (2015)
[9] R. Menditto et al. (2015) submitted
Keywords (Index Terms) — ϕ Josephson junction, butterfly effect, bi-stability, superconductor, ferromagnet.
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), January 2016. 
Received January 15, 2016, Selected January 19, 2016.  Reference No. STP497; Category 4.
KRYO 2015 oral presentation. Not submitted for publication.