First-principles prediction of the two-dimensional intrinsic ferrovalley material CeX2 (X=F,Cl,Br)

Two-dimensional (2D) ferrovalley semiconductor materials with intrinsic spontaneous valley polarization offer new prospects for valley electronics applications. However, there are only a limited number of known promising candidate materials, which are in urgent need of expansion. In particular, the room-temperature 2D ferrovalley materials are still lacking. In this study, we predicted novel 2D ferromagnetic CeX2 (X=Fe,Cl,Br) monolayers by using first-principles calculations. The monolayer CeX2 is a bipolar magnetic semiconductor with robust dynamical and thermal stabilities, and easy magnetization direction is in the plane. Due to the simultaneous breaking of both inversion symmetry and time-reversal symmetry, the monolayer CeX2 is exhibiting a spontaneous intrinsic valley polarization when magnetized along the out-of-plane z direction. Interestingly, monolayer CeBr2 is a spontaneous intrinsic ferrovalley material with a room temperature of 334 K and an obvious valley splitting of 32 meV. Due to the non-zero valley-contrast Berry curvature, monolayer CeBr2 is a candidate materials for realizing the anomalous valley Hall effect under a suitable applied electric field. Our study provides a theoretical reference for the design of valley electronic devices with anomalous valley Hall effect based on hole-doped CeX2.

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