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 mu(F) of the F regions or varies the angle theta between exchange field orientations. Superconductivity can then be switched on and off by varying either theta or mu(F) (a spin-controlled superconducting graphene switch). The induced equal-spin triplet correlations in S can be controlled by tuning mu(F), effectively making a graphene based two-dimensional spin-triplet valve.