Magnetic and ferroelectric control over spontaneous valley polarization in ScO2RuCl-based room-temperature ferrovalley and multiferroic semiconductors

The reversible manipulation of spontaneous room-temperature (RT) valley polarization bears great promise in nonvolatile information storage and processing, yet such experimental realization remains an unresolved challenge. By first-principles and Monte Carlo simulations, monolayer ScO${}_2$RuCl is predicted to be an ideal ferrovalley semiconductor with robust Ising ferromagnetism above-RT against the in-plane biaxial strains reachable in experiments, whose nonvolatile valley polarization in the ultraclean limit higher one order of magnitude than RT thermal disturbance can be inverted by spin-flip transition. The spin–orbital coupling Hamiltonian quite well captures the switchable valley physics. More intriguingly, we appreciate convertible above-RT out-of-plane ferroelectric polarization through interlayer sliding in bistable A-type Ising antiferromagnetically coupled ScO${}_2$RuCl bilayers with an ultralow switching barrier and an ultrahigh Néel temperature. Resultant giant sliding ferroelectricity can manipulate the saturated valley polarization unprecedentedly up to the monolayer limit in a reversible and nonvolatile means. These native RT merits are further found to be immune to moderate compressive strains along the out-of-plane direction. Overall, the switchable valley polarization in response to the direction of either magnetization or ferroelectricity under complicated mechanical environments endows the appealing ScO${}_2$RuCl-based ferrovalley and multiferroic semiconductors with tremendous potential for direct commercial applications of RT polarized electronics.