Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 11: Superconductivity: Tunneling, Josephson Junctions, SQUIDs
TT 11.2: Vortrag
Montag, 25. Februar 2008, 15:45–16:00, H 3010
Tailored Josephson phase: 0, π and 0–π SIFS Josephson junctions — •Martin Weides1, Alexey Bannykh1, Uthayasankaran Peralagu1, Judith Pfeiffer2, Matthias Kemmler2, Dieter Koelle2, Reinhold Kleiner2, and Edward Goldobin2 — 1Institute for Solid State Research, Research Centre Jülich — 2Physikalisches Institut - Experimentalphysik II,
In superconducting/ferromagnet (S/F) systems the superconducting wave function extends into the ferromagnet with a damped oscillatory behavior. This results in novel and interesting physics, such as the possibility to realize a π Josephson junction (JJ) — a JJ with the phase drop of π in the ground state. Recently, we fabricated Nb/Al2O3/NiCu/Nb
JJs with uniform as well as step-like ferromagnetic layer to obtain 0, π and 0-π JJs[1,2].
Here we present our recent results on planar SIFS JJs with F-layer made of Ni, and compare them with the theory in the clean/dirty limit and with experiments by other groups. The critical current density in the π state is larger and the order parameter decay is weaker than for π JJs made using weak ferromagnetic alloys, e.g. NiCu.
The 0–π boundary in JJs with a step-like F-layer thickness may give rise to a pinned spontaneous vortex of supercurrent with magnetic flux ≤|Φ0/2|. Latest experiments on short and long stepped SIFS JJs (0–π, 0–π–0 etc.) will be discussed.
[1] M. Weides et al., Phys. Rev. Lett. 97, 247001 (2006)
[2] M. Weides et al., Appl. Phys. A 89, 613–617 (2007)