  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.
