Signatures of a long-range spin-triplet component in an Andreev interferometer

Abstract

We analyze the Josephson IJ and dissipative Idis currents in a magnetic Andreev interferometer in the presence of the long-range spin triplet component (LRSTC). The Andreev interferometer has a crosslike geometry and consists of a SFl−F−FrS circuit and perpendicular to it a N-F-N circuit, where S, Fl,r are superconductors and weak ferromagnets with noncollinear magnetizations Ml,r, and F is a ferromagnet with a high exchange energy. The ferromagnetic wire F can be replaced with a nonmagnetic wire n. In the limit of a weak proximity effect (PE), we obtain simple analytical expressions for the currents IJ=Ic(α,β)sinφ and Idis=IV(α,β)cosφ. In particular, the critical Josephson current in a long Josephson junction (JJ) is Ic(α,β)=Ic0χ(α,β), where the function χ(α,β) is a function of angles (α,β)l,r that characterize the orientations of Ml,r. The oscillating part of the dissipative current Iosc(V)=χ(α,β)cosφIV0(V) in the N-F/n-N circuit depends on the angles (α,β)l,r in the same way as the critical Josephson current Ic(α,β) but can be much greater than the Ic(α,β). At some angles the current Ic(α,β) changes sign. We briefly discuss a relation between the negative current Ic(α,β) and paramagnetic response. We argue that the measurements of the conductance in the N-F/n-N circuit can be used as another complementary method to identify the LRSTC in S/F heterostructures.

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