Twist and Magnetic Proximity Control of Valley Polarization in WSe2/WS2 Moire Heterostructures

Twist engineering and magnetic proximity provide complementary handles for controlling valley degrees of freedom in two-dimensional transition-metal dichalcogenide heterostructures. Here, we propose VS2/WSe2/WS2 trilayers as a moiré magnetic-proximity platform for moiré-modulated valley and optical responses. First-principles calculations show that pristine WSe2/WS2 heterobilayers at θ = 60° and 21.79° possess type-II band alignment, with WSe2-dominated valence edges and WS2-dominated conduction edges. Although their Berry curvature is valley contrasting, time-reversal symmetry preserves K/K′ degeneracy. Placing ferromagnetic VS2 on the WSe2 side introduces proximity exchange into the WSe2-dominated valence states, producing valence-band valley splittings of −10.971, −4.115, and +1.088 meV for θ = 60°, 21.79°, and 13.17°, respectively. The variation among these commensurate structures indicates that the proximity-induced valley splitting is sensitive to the overall moiré configuration, including local stacking and interlayer hybridization, rather than to twist angle alone. The calculated circular optical response further exhibits helicity-dependent absorption and finite optical selectivity, suggesting a route to moiré-controllable valley-optoelectronic functionality.