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TT: Tiefe Temperaturen
TT 10: Superconductivity - Tunneling, Josephson Junctions, SQUIDs
TT 10.4: Talk
Saturday, March 5, 2005, 09:15–09:30, TU H104
Arbitrary fractional Josephson vortices — •Edward Goldobin, Dieter Koelle und Reinhold Kleiner — Physikalische Institut – Experimentalphysik II, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen
Recently we have suggested and demonstrated experimentally that one can create an arbitrary κ-discontinuity in a long Josephson junction (LJJ) made of conventional superconductors, such as Nb, using a pair of tiny current injectors[1]. In this way one can create and study arbitrary fractional vortices which carry the flux 0…Φ0 proportional to κ or to 2π−κ. While for semifluxons (κ=π) a vortex and an antivortex are mirror symmetric, for arbitrary κ-vortices the symmetry is broken. We study several simplest ground states and investigate the boundaries of their stability.
Since κ-vortices are pinned (for κ≠ 2π n) they cannot be moved by a Lorentz force which is induced by an applied bias current — the bias current only changes the shape of κ-vortex. If the bias current is removed, the vortex returns to its original shape performing decaying oscillations around its equilibrium shape. The frequency of these oscillations can be calculated and depends on κ. Using several coupled κ-vortices at some distance from each other one can design artificial “molecules” and 1D “crystals” with programmable eigen-frequencies (energy-bands) with typical frequencies somewhat below the Josephson plasma frequency.
[1] E. Goldobin et al., Phys. Rev. Lett. 92 057005 (2004).