Ferrovalley Physics in Stacked Bilayer Altermagnetic Systems

As an emerging magnetic phase, altermagnets with compensated magnetic order and nonrelativistic spin-splitting have attracted widespread attention. Currently, strain engineering is considered to be an effective method for inducing valley polarization in altermagnets; however, achieving controllable switching of valley polarization is extremely challenging. Herein, combined with the tight-binding model and first-principles calculations, we propose that interlayer sliding can be used to successfully induce and effectively manipulate the large valley polarization in altermagnets. Using the Fe₂MX₄ (M = Mo, W; X = S, Se, or Te) family as examples, we predict that sliding-induced ferrovalley states in such systems can exhibit many unique properties, including the linearly optical dichroism that is independent of spin-orbit coupling and the anomalous valley Hall effect. These findings imply the correlation among spin, valley, layer, and optical degrees of freedom that makes altermagnets attractive in spintronics, valleytronics, and even their crossing areas.