Spin–vorticity coupling in viscous electron fluids

Ruben J Doornenbal,Marco Polini,R A Duine

doi:10.1088/2515-7639/aaf8fb

Abstract

We consider spin–vorticity coupling—the generation of spin polarization by vorticity—in viscous two-dimensional electron systems with spin–orbit coupling. We first derive hydrodynamic equations for spin and momentum densities in which their mutual coupling is determined by the rotational viscosity. We then calculate the rotational viscosity microscopically in the limits of weak and strong spin–orbit coupling. We provide estimates that show that the spin–orbit coupling achieved in recent experiments is strong enough for the spin–vorticity coupling to be observed. On the one hand, this coupling provides a way to image viscous electron flows by imaging spin densities. On the other hand, we show that the spin polarization generated by spin–vorticity coupling in the hydrodynamic regime can, in principle, be much larger than that generated, e.g. by the spin Hall effect, in the diffusive regime.

Highlights

Introduction.—The field of spintronics is concerned with electric control of spin currents [1]
We show that the spin polarization generated by spin-vorticity coupling in the hydrodynamic regime can, in principle, be much larger than that generated, e.g. by the spin Hall effect, in the diffusive regime
Very recent experimental developments have brought about solid-state systems, such as ultra-clean encapsulated graphene, in which the momentum scattering time can be much longer than the time scale for electronelectron interactions [4,5,6,7]

Summary

Introduction

Introduction.—The field of spintronics is concerned with electric control of spin currents [1]. We first derive hydrodynamic equations for spin and momentum densities in which their mutual coupling is determined by the rotational viscosity. We calculate the rotational viscosity microscopically in the limits of weak and strong spin-orbit coupling.

Results

Conclusion