  Full experimental control of local spin-charge interconversion is of primary
interest for spintronics. Heterostructures combining graphene with a strongly
spin-orbit coupled two-dimensional (2D) material enable such functionality by
design. Electric spin valve experiments have provided so far global information
on such devices, while leaving the local interplay between symmetry breaking,
charge flow across the heterointerface and aspects of topology unexplored.
Here, we utilize magneto-optical Kerr microscopy to resolve the gate-tunable,
local current-induced spin polarisation in graphene/WTe$_2$ van der Waals (vdW)
heterostructures. It turns out that even for a nominal in-plane transport,
substantial out-of-plane spin accumulation is induced by a corresponding
out-of-plane current flow. We develop a theoretical model which explains the
gate- and bias-dependent onset and spatial distribution of the massive Kerr
signal on the basis of interlayer tunnelling, along with the reduced point
group symmetry and inherent Berry curvature of the heterostructure. Our
findings unravel the potential of 2D heterostructure engineering for harnessing
topological phenomena for spintronics, and constitute an important further step
toward electrical spin control on the nanoscale.
