Dual-Polarization Valley Features in a Sc-Doped FeCl₂ Monolayer under Strain

Two-dimensional valley materials have gained extensive interest for their potential applications in valleytronics, while large spontaneous valley polarization usually occurs in either the conduction or valence bands of most previously reported materials. Herein, through the first-principles calculations, we propose that rare dual-polarization valley features can be achieved in both the conduction and valence bands of an FeCl2 monolayer by transition metal doping. Electrons and holes with opposite spins would occupy these valley-polarized energy levels, and thus, a spin valley Hall device with high efficiency and low energy consumption can be designed. Especially for the Sc-doped case, there are no impurity states in the band gap, beneficial for its practical applications. Moreover, the valley polarization in the Sc-doped FeCl2 monolayer can be further engineered by biaxial strain. Our finding can benefit the modulation of the valley physics.