  Unique electronic spin textures in topological states of matter are promising
for emerging spin-orbit driven memory and logic technologies. However, there
are several challenges related to the enhancement of their performance,
electrical gate-tunability, interference from trivial bulk states, and
heterostructure interfaces. We address these challenges by integrating
two-dimensional graphene with a three-dimensional topological insulator (TI) in
van der Waals heterostructures to take advantage of their remarkable spintronic
properties and engineer proximity-induced spin-charge conversion phenomena. In
these heterostructures, we experimentally demonstrate a gate tunable
spin-galvanic effect (SGE) at room temperature, allowing for efficient
conversion of a nonequilibrium spin polarization into a transverse charge
current. Systematic measurements of SGE in various device geometries via a spin
switch, spin precession, and magnetization rotation experiments establish the
robustness of spin-charge conversion in the Gr-TI heterostructures.
Importantly, using a gate voltage, we reveal a strong electric field tunability
of both amplitude and sign of the spin-galvanic signal. These findings provide
an efficient route for realizing all-electrical and gate-tunable spin-orbit
technology using TIs and graphene in heterostructures, which can enhance the
performance and reduce power dissipation in spintronic circuits.
