Spin superfluid Josephson oscillator

TL;DR

This paper proposes a novel spin superfluid Josephson oscillator device that leverages the magnetic analogue of the Josephson effect, demonstrating large output power and potential for neuromorphic computing applications.

Contribution

It introduces the concept and analysis of spin superfluid Josephson oscillators using exchange-coupled ferromagnets separated by a normal metal spacer, highlighting their unique properties.

Findings

Large output power due to maximum magnetoresistance at 2π precession

Presence of Shapiro-like steps under ac current

Potential for neuromorphic computing via multistate mode-locking

Abstract

The magnetic analogue of the Josephson effect can be exploited to develop a new class of nano-spin oscillators that we denote as spin superfluid Josephson oscillators. Such a device, consisting of two exchange coupled easy-plane metallic ferromagnets separated by a thin normal metal spacer, is proposed and analyzed. A spin chemical potential difference drives a $2\pi$ precession of the in-plane magnetization of each ferromagnet. The $2 \pi$ precession angle gives maximum values of the giant magnetoresistance, resulting in large output power compared to conventional spin Hall oscillators. An applied ac current results in a time-averaged magnetoresistance with Shapiro-like steps. The multistate mode-locking behavior exhibited by the spin Shapiro steps may be explored for applications in neuromorphic computing. As an experimental characterization method, electrical measurements of spin superfluid Josephson junctions can provide additional signatures of spin superfluidity.