Double proximity effect in hybrid planar Superconductor-(Normal metal/Ferromagnet)-Superconductor structures

TL;DR

This study investigates the differential resistance in hybrid superconductor-normal/ferromagnet-superconductor structures, revealing a double-peak feature linked to electron spin polarization, which disappears at zero magnetization.

Contribution

It demonstrates the double-peak peculiarity in differential resistance is caused by electron spin polarization induced by the ferromagnet, a novel insight into spin effects in such structures.

Findings

Double-peak in differential resistance at the minigap voltage.

Double-peak converts to a single peak at zero magnetization.

Double-peak is attributed to electron spin polarization.

Abstract

We have investigated the differential resistance of hybrid planar Al-(Cu/Fe)-Al submicron bridges at low temperatures and in weak magnetic fields. The structure consists of Cu/Fe-bilayer forming a bridge between two superconducting Al-electrodes. In superconducting state of Al-electrodes, we have observed a double-peak peculiarity in differential resistance of the S-(N/F)-S structures at a bias voltage corresponding to the minigap. We claim that this effect (the doubling of the minigap) is due to an electron spin polarization in the normal metal which is induced by the ferromagnet. We have demonstrated that the double-peak peculiarity is converted to a single peak at a coercive applied field corresponding to zero magnetization of the Fe-layer.