Elastic Cotunnelling and Crossed Andreev Reflection in Normal-Superconductor Nanostructures*

Transport experiments were made on normal-superconductor-normal systems where the separation of the normal elements is less than a superconducting coherence length. For this geometry two coherent, nonlocal effects have been predicted. In elastic cotunnelling electrons from one normal element can tunnel to the other through a virtual state in the superconducting gap. In crossed Andreev reflection one electron from each spatially separated normal element join to enter the superconductor as a Cooper pair. We present evidence of these nonlocal effects and show that their spatial dependence agrees with theory.