Enhanced controllable triplet proximity effect in superconducting spin-orbit coupled spin valves with modified superconductor/ferromagnet interfaces

TL;DR

This study demonstrates enhanced control of triplet superconductivity in a Nb/Pt/Co/Pt spin valve by interface engineering and spin-orbit coupling, enabling improved triplet pair creation for superspintronics applications.

Contribution

The paper introduces a method to significantly enhance triplet pair conversion in superconducting spin valves through interface modification and spin-orbit coupling effects.

Findings

Enhanced triplet proximity effect observed with Cu/Au interface layers.

Increased spin-orbit coupling correlates with higher triplet pair creation.

Interface engineering improves superconducting spin valve performance.

Abstract

In a superconductor/ferromagnet hybrid, a magnetically controlled singlet-to-triplet Cooper pair conversion can modulate the superconducting critical temperature. In these triplet superconducting spin valves, such control usually requires inhomogeneous magnetism. However, in the presence of spin-orbit coupling from an interfacial heavy-metal layer, the singlet/triplet conversion rate and thus the critical temperature, can be controlled via the magnetization direction of a single homogeneous ferromagnet. Here, we report significantly enhanced controllable pair conversion to a triplet state in a Nb/Pt/Co/Pt superconducting spin valve in which Pt/Co/Pt is homogeneously magnetized and proximity-coupled to a superconducting layer of Nb. The Co/Pt interface furthest away from Nb is modified by a sub-nanometer-thick layer of Cu or Au. We argue that the enhancement is most likely associated from an improvement of the Co/Pt interface due to the insertion of Cu and Au layers. Additionally, the higher normalized orbital moments in Au measured using X-ray magnetic circular dichroism shows that increasing spin-orbit coupling enhances the triplet proximity effect - an observation supported by our theoretical calculations. Our results provide a pathway to enhancing triplet pair creation by interface engineering for device development in superspintronics.