Curvature control of the superconducting proximity effect in diffusive ferromagnetic nanowires

TL;DR

This paper demonstrates that the superconducting critical temperature in superconductor-ferromagnet nanowires can be controlled solely by adjusting the curvature of the ferromagnetic component, enabling a new form of triplet spin-valve effect.

Contribution

It introduces a novel method to tune the superconducting proximity effect via geometric curvature without additional ferromagnets or spin-orbit coupling.

Findings

Critical temperature varies with curvature of the ferromagnetic nanowire.

Curvature control enables a robust triplet spin-valve effect.

Spin-orbit coupling modifies the effect both quantitatively and qualitatively.

Abstract

Coupling a conventional s-wave superconductor to a ferromagnet allows, via the proximity effect, to generate superconducting triplet correlations. This feature can be employed to achieve a superconducting triplet spin-valve effect in superconductor-ferromagnet (SF) hybrid structures, for example by switching the magnetizations of the ferromagnets between parallel and antiparallel configurations in F1SF2 and SF1F2 trilayers, or in SF bilayers with both Rashba and Dresselhaus SOC. It was recently reported that geometric curvature can control the generation of long ranged triplets. We use this property to show that the superconducting critical temperature of an SF hybrid nanowire can be tuned by varying the curvature of the ferromagnetic side alone, with no need of another ferromagnet or SOC. We show that the variation of the critical temperature as a function of the curvature can be exploited to obtain a robust, curvature-controlled, superconducting triplet spin-valve effect. Furthermore, we perform an analysis with the inclusion of spin-orbit coupling and explain how it modifies the spin-valve effect both quantitatively and qualitatively.