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要旨

We investigated the electronic structure of the layered transition-metal dichalcogenides VS2 and VSe2 by first-principles calculations. Both compounds exhibit metal-insulator transitions when crossing over from the bulk to the two-dimensional monolayer. In the monolayer limit, the Coulomb interaction is enhanced due to the dimension reduction, leading to the insulating state. Moreover, these monolayers are found to be ferromagnetic, supplying excellent candidates for ferromagnetic insulators. When increasing the thickness, the few-layer structure turns metallic and presents large anomalous Hall conductivity (similar to 100 S/cm), which oscillates with respect to the thickness due to the size effect. Our findings presents profound materials, such as ferromagnetic insulators and anomalous Hall ferromagnets, for the spintronic application.