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Regular version of the site

Article

Сooper pair splitting in ballistic ferromagnetic SQUIDs

Physical Review B: Condensed Matter and Materials Physics. 2017. Vol. 96. No. 17. P. 174508-1-174508-13.
Stroganov P. L., Ya.V. Fominov.

WeconsiderballisticSQUIDswithspinfilteringinsidehalf-metallicferromagneticarms.AsingletCooperpair
cannot pass through an arm in this case, so the Josephson current is entirely due to the Cooper pair splitting, with
two electrons going to different interferometer arms. In order to elucidate the mechanisms of Josephson transport
due to split Cooper pairs, we assume the arms to be single-channel wires in the short-junction limit. Different
geometries of the system (determined by the length of the arms and the phases acquired by quasiparticles during
splitting between the arms) lead to qualitatively different behavior of the SQUID characteristics (the Andreev
levels, the current-phase relation, and the critical Josephson current) as a function of two control parameters,
the external magnetic flux and misorientation of the two spin filters. The current-phase relation can change its
amplitudeandshape,inparticular,turningtoaπ junctionformoracquiringadditionalzerocrossings.Thecritical
current can become a nonmonotonic function of the misorientation of the spin filters and the magnetic flux (on
half of period). Periodicity with respect to the magnetic flux is doubled, in comparison to conventional SQUIDs.