Semifluxon

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In superconductivity, a Semifluxon is a vortex of supercurrent carrying the magnetic flux equal to the half of the magnetic flux quantum. Semifluxons exist in the so-called 0-π long Josephson junctions at the boundary between 0 and π regions. For a shorter junction length (approx. Josephson penetration depth λ_J) the vortex does not fit into the junction and the flux inside the junction is reduced. In that case one refers to a fractional flux quantum instead of half a flux quantum or semifluxon.

For the first time semifluxons were observed using d-wave superconductors at so called tricrystal grain boundaries and later in YBa₂Cu₃O₇–Nb ramp zigzags. In these systems the phase shift of π takes place inside the d-wave superconductor and not at the barrier. Due to the advent of controlled coupling by proper chosen ferromagnetic thicknesses, 0–π JJs have also recently been realized in low-T_c SFS-like systems ^[1] and underdamped SIFS-type ^[2].

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[edit] References

J. H. Xu, J. H. Miller, Jr., and C. S. Ting (1994). "π-vortex state in a long 0-π Josephson junction". Phys. Rev. B 51: 11958. DOI:10.1103/PhysRevB.51.11958.

E. Goldobin, D. Koelle, R. Kleiner (2002). "Semifluxons in long Josephson 0-π-junctions". Phys. Rev. B 66: 100508. DOI:10.1103/PhysRevB.66.100508.

C. C. Tsuei and J. R. Kirtley (2002). "d-Wave pairing symmetry in cuprate superconductors --- fundamental implications and potential applications". Physica C 367: 1.

H. Hilgenkamp, Ariando, H.-J. H. Smilde, D. H. A. Blank, G. Rijnders, H. Rogalla, J. R. Kirtley and C. C. Tsuei, (2003). "Ordering and manipulation of the magnetic moments in large-scale superconducting π-loop arrays". Nature (London) 442: 50.

and

^ M. L. Della Rocca, M. Aprili, T. Kontos, A. Gomez and P. Spathis (2005). "Ferromagnetic 0-π Junctions as Classical Spins". Phys. Rev. Lett 94: 197003. DOI:10.1103/PhysRevLett.94.197003.
^ M. Weides, M. Kemmler, H. Kohlstedt, R. Waser, D. Koelle, R. Kleiner and E. Goldobin (2006). "0-π Josephson Tunnel Junctions with Ferromagnetic Barrier". Phys. Rev. Lett 97: 247001. DOI:10.1103/PhysRevLett.97.247001.