Long range Josephson coupling through ferromagnetic graphene

Abstract

We study the Josephson effect in graphene-based ballistic superconductor-ferromagnet-superconductor (SFS) junctions. We find an oscillatory Josephson coupling $I_c{R}_N$ of F graphene whose amplitude is nonvanishing for a half-metallic graphene, increases for the exchange fields $h$ above the Fermi energy $E_F$ and shows only a slow damping at strong exchange fields $h\gg E_F$. 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 $E_F$. We further demonstrate the existence of regular temperature induced transitions between 0 and $\pi$ couplings in the plane of $T$ and $h$ where the phase boundaries have distinct shapes at the two regimes of $h$ below and above $E_F$.

4 pages, 2 figures

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Cited by in corpus (1)

• Andreev-Klein reflection in graphene ferromagnet-superconductor junctions