Long-range Josephson coupling through ferromagnetic graphene

Ali G. Moghaddam; Malek Zareyan

doi:10.1103/PhysRevB.78.115413

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Long-range Josephson coupling through ferromagnetic graphene

Ali G. Moghaddam, Malek Zareyan

DOI 10.1103/PhysRevB.78.115413 · Physical Review B

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Abstract

We study the Josephson effect in graphene-based ballistic superconductor-ferromagnet-superconductor (SFS) junctions. We find an oscillatory Josephson coupling IcRN of F graphene whose amplitude is nonvanishing for a half-metallic graphene, increases for the exchange fields h above the Fermi energy EF and shows only a slow damping at strong exchange fields h⪢EF. We interpret this long-range Josephson coupling as the result of the exchange mediated Andreev-Klein process at FS interfaces which enhances the induced antiparallel-spin superconducting correlations in F graphene by increasing h above EF. We further demonstrate the existence of regular temperature-induced transitions between 0 and π couplings in the plane of T and h where the phase boundaries have distinct shapes at the two regimes of h below and above EF.