Tunable Ferroelectricity, Valley Polarization, Layer Polarization, and Magnetism Via Stacking in 2D van der Waals Bilayers

Magnetic two-dimensional van der Waals (vdWs) materials hold potential applications in low-power and high-speed spintronic devices due to their degrees of freedom such as valley and spin. In this Letter, we propose a mechanism that uses stacking engineering to control valley polarization (VP), ferroelectricity, layer polarization (LP), and magnetism in vdWs bilayers. Through first-principles calculations, we predict that the T-VSI monolayer is a magnetic semiconductor with a sizable VP. Interestingly, the T-VSI bilayer can realize the control of VP, ferroelectricity, LP, and magnetism through interlayer sliding and twisting. More importantly, we further explain the mechanisms of the magnetic phase transition and LP by using interlayer electron hopping and the k·p model, respectively. Our scheme provides a platform for designing and manipulating vdWs systems with multiple degrees of freedom.