# Semi-Quantized Spin Pumping and Spin-Orbit Torques in Topological Dirac Semimetals

## TL;DR

This paper investigates spin and charge transport in topological Dirac semimetals, revealing semi-quantized charge currents and efficient spin-charge conversion mechanisms driven by topological properties.

## Contribution

It demonstrates that topological Dirac semimetals exhibit semi-quantized charge currents and enhanced spin-orbit torques, offering a new platform for low-dissipation spintronic devices.

## Key findings

- Large inverse spin Hall effect in Dirac semimetals
- Charge current depends only on Dirac point separation
- Electric field induces spin torque via semi-quantized spin Hall effect

## Abstract

We study the time-development processes of spin and charge transport phenomena in a topological Dirac semimetal attached to a ferromagnetic insulator with a precessing magnetization. Compared to conventional normal metals, topological Dirac semimetals manifest a large inverse spin Hall effect when a spin current is pumped from the attached ferromagnetic insulator. It is shown that the induced charge current is semi-quantized, i.e., it depends only on the distance between the two Dirac points in momentum space and hardly depends on the disorder strength when the system remains in the topological Dirac semimetal phase. As an inverse effect, we show that the electric field applied to the topological Dirac semimetal exerts a spin torque on the local magnetization in the ferromagnetic insulator via the exchange interaction and the semi-quantized spin Hall effect. Our study demonstrates that the topological Dirac semimetal offers a less-dissipative platform for spin-charge conversion and spin switching.