Spin-controlled superconductivity and tunable triplet correlations in graphene nanostructures

We study graphene ferromagnet/superconductor/ferromagnet (F/S/F) nanostructures via a microscopic self-consistent Dirac Bogoliubov-de Gennes formalism. We show that as a result of proximity effects, experimentally accessible spin switching phenomena can occur as one tunes the Fermi level μ_F of the F regions or varies the angle θ between exchange field orientations. Superconductivity can then be switched on and off by varying either θ or μ_F (a spin-controlled superconducting graphene switch). The induced equal-spin triplet correlations in S can be controlled by tuning μ_F, effectively making a graphene based two-dimensional spin-triplet valve.