  We report on fundamental aspects of spin dynamics in graphene interfaced with
transition metal dichalcogenides (TMDCs). By using realistic models derived
from first principles we compute the spin lifetime anisotropy, defined as the
ratio of lifetimes for spins pointing out of the graphene plane to those
pointing in the plane. In the presence of strong intervalley scattering the
anisotropy can reach unprecedented values of tens to hundreds, while it reduces
to 1/2 for weak disorder. This behavior is mediated by spin-valley locking,
which is strong in TMDCs and is imprinted onto graphene. Such giant spin
transport anisotropy, driven by proximity effects, provides an exciting
paradigm for designing novel spin device functionalities.
