Tunable valley polarization and magnetic coupling by ferroelectric substrate in a VSe2/AgBiP2Se6 heterostructure

Valleytronics, exploring the valley degree of freedom in crystals akin to the charge in electronics and spin in spintronics, holds tremendous potential for information processing and computing in next-generation devices. We investigated the spin and valley manipulation of a $2H$-${\text{VSe}}_{2}$ monolayer by stacking a ferroelectric substrate, ${\text{AgBiP}}_{2}{\text{Se}}_{6}$, to form a van der Waals heterostructure, ${\text{VSe}}_{2}/{\text{AgBiP}}_{2}{\text{Se}}_{6}$, whose lattice mismatch is only 0.44%. Because the band alignment between ${\text{VSe}}_{2}$ and ${\text{AgBiP}}_{2}{\text{Se}}_{6}$ is type I, the valley property at both the valence band and conduction band is well maintained, and the heterostructure exhibits an anomalous valley Hall effect. By switching the ferroelectric polarization direction, valley polarization can be effectively tuned, and the manipulation is nonvolatile because the heterostructure holds the ferroelectric bistability property. When the ferroelectric polarization points to ${\text{VSe}}_{2}$, interlayer sliding can give rise to obvious valley polarization changes with a small sliding potential, and by interlayer charge transfer, the exchange coupling of $\mathrm{V}$ atoms can be obviously tuned, and therefore the Curie temperature is enhanced from 680 K to 975 K.