  A charge density wave (CDW) represents an exotic state in which electrons are
arranged in a long range ordered pattern in low-dimensional materials. Although
our understanding of the fundamental character of CDW has been enriched after
extensive studies, its relationship with functional phenomena remains
relatively limited. Here, we show an unprecedented demonstration of a tunable
charge-spin interconversion (CSI) in graphene/1T-TaS$_2$ van der Waals
heterostructures by manipulating the distinct CDW phases in 1T-TaS$_2$. Whereas
CSI from spins polarized in all three directions are observed in the
heterostructure when the CDW phase does not show commensurability, the output
of one of the components disappears and the other two are enhanced when the CDW
phase becomes commensurate. The experimental observation is supported by
first-principles calculations, which evidence that chiral CDW multidomains are
at the origin of the switching of CSI. Our results uncover a new approach for
on-demand CSI in low-dimensional systems, paving the way for advanced
spin-orbitronic devices.
