Negative four-terminal resistance as a probe of crossed Andreev reflection

TL;DR

This paper experimentally investigates superconductor-ferromagnet structures, revealing negative four-terminal resistance caused by crossed Andreev reflection, which enhances understanding of quantum transport phenomena in hybrid systems.

Contribution

It provides the first experimental evidence of negative four-terminal resistance as a signature of crossed Andreev reflection in superconductor-ferromagnet devices.

Findings

Negative four-terminal resistance observed below the superconducting gap.

Evidence supports crossed Andreev reflection as the underlying mechanism.

Results advance understanding of quantum transport in hybrid superconductor-ferromagnet systems.

Abstract

We report on the experimental investigation of electronic transport in superconductor-ferromagnet spin-valve structures. Our samples consist of two ferromagnetic iron leads forming planar tunnel contacts to a superconducting aluminum wire. At energies below the superconducting gap, we observe a negative four-probe resistance that can be explained by crossed Andreev reflection.