Charge-to-spin conversion in atomically thin bismuth

We report charge-to-spin conversion in a hybrid heterostructure comprised of atomically thin bismuth (Bi) confined between a silicon carbide (SiC) substrate and epitaxial graphene (EG). We confirm the composition, the dimensionality, and a 96.5% intercalation coverage using x-ray photoelectron spectroscopy, scanning transmission microscopy, low-energy electron diffraction, and Raman spectroscopy. Electrical transport measurements show signs of weak antilocalization in the heterostructure. Spin-torque ferromagnetic resonance measurements in Permalloy/EG/2D-Bi heterostructures probe charge-to-spin conversion, revealing an in-plane polarization of the spin current, perpendicular to the charge current. The ratio of the in-plane to out-of-plane torque is 3.75 times higher than in hydrogenated graphene control samples.