Experimental Evidence for Crossed Andreev Reflection

TL;DR

This paper provides experimental evidence for crossed Andreev reflection in superconductor-ferromagnet structures, demonstrating non-local resistance effects and electron-hole entanglement at mesoscopic scales.

Contribution

It presents the first experimental observation of crossed Andreev reflection in ferromagnet-superconductor devices with planar tunnel contacts.

Findings

Negative non-local resistance observed

Evidence supports crossed Andreev reflection process

Electron-hole entanglement demonstrated

Abstract

We report on electronic transport properties of mesoscopic superconductor-ferromagnet spin-valve structures. Two ferromagnetic iron leads form planar tunnel contacts to a superconducting aluminum wire, where the distance of the two contacts is of the order of the coherence length of the aluminum. We observe a negative non-local resistance which can be explained by crossed Andreev reflection, a process where an electron incident from one of the leads gets reflected as a hole into the other, thereby creating a pair of spatially separated, entangled particles.