# Theory of spin hydrodynamic generation

## TL;DR

This paper develops a theoretical framework for spin-current generation in fluid flows, linking fluid vorticity to spin currents, and predicts measurable inverse spin Hall voltages in laminar and turbulent regimes, advancing fluid spintronics.

## Contribution

It introduces a quantum kinetic theory-based model coupling spin diffusion with fluid vorticity, predicting spin current generation in various flow conditions.

## Key findings

- Spin currents are generated by vorticity gradients in fluid flows.
- Inverse spin Hall voltage is proportional to flow velocity in laminar flow.
- Voltage scales with the square of flow velocity in turbulent flow.

## Abstract

Spin-current generation by fluid motion is theoretically investigated. Based on quantum kinetic theory, the spin-diffusion equation coupled with fluid vorticity is derived. We show that spin currents are generated by the vorticity gradient in both laminar and turbulent flows and that the generated spin currents can be detected by the inverse spin Hall voltage measurements, which are predicted to be proportional to the flow velocity in a laminar flow. In contrast, the voltage in a turbulent flow is proportional to the square of the flow velocity. This study will pave the way to fluid spintronics.