Room-temperature multiferroic semiconductor with electrically switchable valley polarization in Zn-/Cd-intercalated $\mathrm{CrSe_2}$

Purely electrical switching of ferromagnetism-induced valley polarization in two dimensional (2D) ferrovalley materials provides a promising avenue for low-power information processing. Herein, Zn- and Cd-intercalated CrSe _{2} 2 (denoted XCrSe _{2} 2 , X = Zn, Cd) are predicted by first-principles calculations to be room-temperature ferrovalley semiconductors, in which valley polarization can be switched by reversing the ferroelectric (FE) polarization. The intercalated atoms break inversion symmetry and generate in-plane and out-of-plane FE polarizations with low switching barriers and polar distortions stable above room temperature in AIMD simulations. The superexchange of t_{2g} t 2 g and e_g e g of Cr atoms dominates the ferromagnetic (FM) coupling with Curie temperature near 350 K and out-of-plane easy axis. The ferromagnetism together with spin-orbit coupling lifts the K/K ' ′ valley degeneracy and produces spin-polarized valley splitting. Crucially, FE reversal strongly modifies the electronic structure and valley-resolved states, enabling electrical control of the valley splitting, and ferroelectrically switchable anomalous valley Hall effect in a single material platform. Our results establish monolayer XCrSe _2 2 as a rare 2D multiferroic semiconductor combining robust FE and FM orders with nonvolatile electrical control of valley degrees of freedom.