Regensburg 2004 – scientific programme
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TT: Tiefe Temperaturen
TT 31: Supraleitung: Vortexdynamik, Vortexphasen, Pinning
TT 31.2: Talk
Friday, March 12, 2004, 10:30–10:45, H20
Study of semifluxons in artificial long Josephson 0-π-junctions — •Tobias Gaber1, Edward Goldobin1,2, Albert Sterck1, Dieter Koelle1, and Reinhold Kleiner1 — 1Physikalisches Institut, Experimentalphysik II, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen — 2Institut für Mikro- und Nanoelektronische Systeme, Universität Karlsruhe (TH), Hertzstr. 16, D-76187 Karlsruhe
In long Josephson junctions (LJJ) consisting of two
parts with positive and negative critical current (0 and π
parts) half-integer vortices (semifluxons) can spontaneously
appear at the boundary between these parts.
Such a boundary
formally corresponds to a π-discontinuity of the Josephson
phase. In our experiments we artificially create such a
discontinuity in conventional Nb-AlOx-Nb LJJs using a pair of
current injectors. Such JJs allow one to study arbitrary
fractional vortices and their dynamics.
In the
0-π-state the Ic(H) dependence shows a minimum at H =
0 as in natural 0-π-LJJs. We investigate the dynamics of
the magnetic flux in such junctions for various lengths and
observe half-integer zero-field steps (ZFS) with n=
1/2,3/2,5/2 on the IV-characteristics
which appear due to the motion of semi-integer flux. We also show
that semi-integer ZFS quantisation persists even when arbitrary
fractional vortices (other that Φ0/2) are participating in
the motion.