Charge imbalance, crossed Andreev reflection and elastic co-tunnelling in ferromagnet/superconductor/normal-metal structures

We examine here electronic transport in nanoscale systems where normal and ferromagnetic probes are attached to a conventional superconductor. While reviewing the long-studied effects of Andreev reflection and charge imbalance, we concentrate on two recently predicted coherent, nonlocal processes known as crossed Andreev reflection and elastic co-tunnelling. These processes can occur when two spatially separated normal or ferromagnetic probes are separated by a distance comparable to the coherence length of the superconductor. Here we show that normal probes, by avoiding some of the experimental and theoretical complications of ferromagnetic probes, may offer a better opportunity to examine these processes.