Spin hydrodynamic generation in unsteady flows

TL;DR

This paper presents a theoretical study of spin hydrodynamic generation in unsteady liquid metal flows, showing that observable voltages can be induced, which could enable high-speed spintronic devices utilizing unsteady fluid flows.

Contribution

It introduces a theoretical framework for spin hydrodynamic generation in unsteady flows, including spin-vorticity coupling, expanding fluid spintronics to dynamic flow conditions.

Findings

Observable voltage can be induced in unsteady liquid metal flows.

Spin-vorticity coupling plays a key role in spin current generation.

Potential for high-speed spintronic devices using unsteady flows.

Abstract

We theoretically investigate a spin-mediated conversion from fluid dynamics to voltage, known as spin hydrodynamic generation (SHDG), in oscillatory and transient unsteady flows. We consider unsteady flows of liquid metal between two parallel infinite planes and then calculate its vorticity fields based on the Navier--Stokes equation for an incompressible viscous fluid. The spin accumulation and spin current generated by unsteady flows are derived using a spin-diffusion equation, including spin-vorticity coupling, which is a couple of angular momentum between electron spin and vorticity field in unsteady flows. The estimation of SHDG in liquid mercury flow suggests that an observable magnitude of voltage can be induced in unsteady flows. Our results are expected to enable the realization of high-speed spin devices with unsteady flows and broaden the range of fluid spintronics applicability.