A key goal of spintronics is replacing charge currents, which suffer from joule heating, with spin currents, which are more efficient and versatile information carriers. However, conventional spin currents are diffusive, undermining their utility. Over the years, spin superfluidity, the magnetic analog of superfluidity and superconductivity, has emerged as a promising means of near-dissipationless spin transport [1, 2]. While researchers have predicted that magnetic films can exhibit spin superfluidity, most theoretical studies considered impractical device setups [3, 4]. Moreover, experimental reports of the phenomenon are few—and none have been unambiguously conclusive [1].

In this talk, I present a path to realizing spin superfluidity (SSF) in practical devices. I begin with an overview how spin currents are typically generated by the spin Hall effect and transmitted via spin waves. I then explain the non-diffusive mechanism behind SSF and outline how SSF can replace spin wave transport in injector–film–detector devices with a fabrication-friendly lateral geometry. After introducing the Landau–Lifshitz–Gilbert equation of magnetization dynamics, I build up a circuit model that describes spin transport and dissipation across the device, highlighting key material properties. Notably, I also demonstrate that SSF is geometrically tunable at arbitrary length scales. Finally, I discuss how probing the resistance of the device reveals the nonlocal nature of the magnetoresistance associated with the spin Hall effect. This work presents a roadmap for harnessing spin superfluidity in magnetic films and unveils unique characteristics of this phenomenon which can serve as conclusive evidence of its existence.

[1] E. B. Sonin, Phys. Rev. B 95, 144432 (2017); Phys. Rev. B 99, 104423 (2019)

[2] D. Hill, S. K. Kim, and Y. Tserkovnyak, Phys. Rev. Lett. 121, 037202 (2018)

[3] S. Takei and Y. Tserkovnyak, Phys. Rev. Lett. 112, 227201 (2014)

[4] H. Skarsvåg, C. Holmqvist, and A. Brataas, Phys. Rev. Lett. 115, 237201 (2015)