Tunable Pure Spin Supercurrents and the Demonstration of Their Gateability in a Spin-Wave Device

Abstract

Recent ferromagnetic resonance experiments and theory of Pt/Nb/Ni_{8}Fe_{2} proximity-coupled structures strongly suggest that spin-orbit coupling (SOC) in Pt in conjunction with a magnetic exchange field in Ni_{8}Fe_{2} are the essential ingredients to generate a pure spin supercurrent channel in Nb. Here, by substituting Pt for a perpendicularly magnetized Pt/Co/Pt spin sink, we are able to demonstrate the role of SOC and show that pure spin supercurrent pumping efficiency across Nb is tunable by controlling the magnetization direction of Co. By inserting a Cu spacer with weak SOC between Nb and Pt/(Co/Pt) spin sink, we also prove that Rashba-type SOC is key for forming and transmitting pure spin supercurrents across Nb. Finally, by engineering these properties within a single multilayer structure, we demonstrate a prototype superconductor spin-wave device in which lateral spin-wave propagation is gateable via the opening or closing of a vertical pure spin supercurrent channel in Nb.