Spin-to-charge conversion in low-symmetry MoTe2/graphene van der Waals heterostructures

Abstract

This Thesis presents an exhaustive study of the spin-to-charge conversion processes that take place in low-symmetry MoTe2/graphene van der Waals heterostructure. While in high-symmetry materials, the spin-to-charge conversion process is limited to the orthogonal configuration, where spin current, charge current and spin polarization are mutually perpendicular, low symmetry materials are expected to present spin-to-charge conversion in different configurations. At moderately high temperatures, along with the orthogonal configuration, in graphene/MoTe2 we also detect an unconventional spin-to-charge conversion arising from the spins polarized parallel to the direction of the charge current. While the former is allowed by the crystal symmetries, for the latter to occur the crystal symmetries of the system must be reduced. Additionally, at low temperatures is observed an extra spin-to-charge contribution from the out-of-plane polarized spins. In addition, using a recently introduce 3D-current configuration, an extra spin-to-charge conversion configuration is observed. The possible origins of these processes are spin Hall effect in MoTe2 or Edelstein effect in the proximitized graphene Regardless of the origin, the observed high efficiencies in the spin-to-charge conversion processes, together with the versatility in the spin-to-charge conversion configurations, postulate graphene/MoTe2 heterostructures as candidates for the required new architecture in spintronic devices.