Correlated transport at multiple superconductor-ferromagnet interfaces

We consider hybrid structures made of two superconducting-normal (or ferromagnetic) contacts. At short distances, reflexion processes across the superconductor, from one contact to the other, can lead to new physical effects. Normal reflexion involves cotunneling, which is spin-conserving, while Andreev reflexions converting an electron into a hole reverse the spin. Here we investigate the transport properties of the structure and emphasize its sensitivity to spin polarizations. An application is given in terms of a principle for a spin-STM.