Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 11: Superconductivity: Tunneling, Josephson Junctions, SQUIDs
TT 11.9: Vortrag
Montag, 25. Februar 2008, 17:45–18:00, H 3010
Controllable manupulation and SQUID readout of two coupled semifluxons (exchanged with TT 11.5) — •Edward Goldobin, Andreas Dewes, Florian Jessen, Dieter Koelle, and Reinhold Kleiner — Physikalisches Institut–Experimentalphysik II and Center for Collective Quantum Phenomena, University of Tübingen, Auf der Morgenstelle 14, 72076, Tübingen, Germany
Josephson vortices carrying half of the magnetic flux quantum Φ0 naturally appear in 0-π long Josephson junctions (LJJs) that can be fabricated using various technologies[1–3]. Such semifluxons are pinned at the 0-π boundary, but may have two polarities that can be used for information processing, i.e. the state ↑, corresponding to the flux +Φ0/2, and the state ↓, corresponding to the flux −Φ0/2. The first proposed prototype of a semifluxon based qubit employs two degenerate ground states ↑↓ and ↓↑ of a two semifluxon molecule in 0-π-0 LJJ[4]. It was predicted that such a molecule may be switched between the states ↑↓ and ↓↑ by applying a small bias current[5].
Using two SQUIDs placed in front of each semifluxon to readout their magnetic flux (polarity), we experimentally demonstrate the ↑↓←→↓↑ transition controlled by uniform dc bias current. We also observe ↑↑ and ↓↓ states and controllably changed them to the ↑↓ and ↓↑ states.
[1] H. Hilgenkamp et al. Nature 422, 50 (2003)
[2] M. Weides et al., Phys. Rev. Lett. 97, 247001 (2006)
[3] E. Goldobin et al., Phys. Rev. B. 72, 054527 (2005)
[4] E. Goldobin et al., Phys. Rev. B 67, 224515 (2003)
[5] E. Goldobin et al., Phys. Rev. B.72, 054527 (2005).