Generation of pure superconducting spin current in magnetic heterostructures via non-locally induced magnetism due to Landau Fermi-liquid effects

TL;DR

This paper introduces a mechanism where Landau Fermi-liquid interactions and spin-orbit coupling in heterostructures generate pure superconducting spin currents via non-local induced magnetism, advancing superconducting spintronics.

Contribution

It reveals how Landau Fermi-liquid interactions enable non-local ferromagnetic exchange fields and spin supercurrents in superconductor heterostructures, a novel insight for superconducting spintronics.

Findings

Long-range spin-triplet correlations are induced in the trilayer.

The spin supercurrent magnitude depends on proximity effects and Fermi-liquid parameters.

The mechanism explains recent experimental observations in superconducting spintronics.

Abstract

We propose a mechanism for the generation of pure superconducting spin-current carried by equal-spin triplet Cooper pairs in a superconductor (S) sandwiched between a ferromagnet (F) and a normal metal (N$_{\rm so}$) with intrinsic spin-orbit coupling. We show that in the presence of Landau Fermi-liquid interactions the superconducting proximity effect can induce non-locally a ferromagnetic exchange field in the normal layer, which disappears above the superconducting transition temperature of the structure. The internal Landau Fermi-liquid exchange field leads to the onset of a spin supercurrent associated with the generation of long-range spin-triplet superconducting correlations in the trilayer. We demonstrate that the magnitude of the spin supercurrent as well as the induced magnetic order in the N$_{\rm so}$ layer depends critically on the superconducting proximity effect between the S layer and the F and N$_{\rm so}$ layers and the magnitude of the relevant Landau Fermi-liquid interaction parameter. We investigate the effect of spin flip processes on this mechanism. Our results demonstrate the crucial role of Landau Fermi-liquid interaction in combination with spin-orbit coupling for the creation of spin supercurrent in superconducting spintronics, and give a possible explanation of a recent experiment utilizing spin-pumping via ferromagnetic resonance [Jeon $\it{ et}$ $\it{al.}$, Nat. Mat. ${\bf 17}$, 499 (2018)].