Crossed Andreev reflection in graphene-based ferromagnet-superconductor structures

We report a theoretical investigation of the spin-polarized transport of relativistic electrons through a three-terminal graphene-based superconductor bipolar transistor with ferromagnetic leads. It is found that the magnetoresistance in such a system can be improved largely in comparison with that in the corresponding two-terminal structure due to the existence of the special crossed Andreev reflection, which is quite different from that in the conventional three-terminal ferromagnet-superconductor devices. The physical origination for such a phenomenon has also been analyzed. We also find that the non-local conductivity can not only exhibit different feature for parallel and antiparallel alignment, it is also easily tuned by the external magnetic field and the bias voltage.