Switchable room-temperature valley polarization in a Janus GeRuO2SiN2 native ferrovalley monolayer and its self-assembled sliding multiferroics

Abstract

Realizing efficient switchability of nonvolatile room-temperature valley polarization in two-dimensional native ferrovalley systems is a pivotal step towards realistic applications in multifunctional integrated devices, yet such progress has scarcely been made thus far. By first-principles calculations and Monte Carlo simulations, we identify the Janus GeRuO₂SiN₂ monolayer as a realizable ferrovalley semiconductor with significant out-of-plane magnetization, ultrahigh Curie temperature and sizable valley polarization in the absence and presence of both hole doping and biaxial strains within experimental reach, thus facilitating the observation of the anomalous valley Hall effect. Upon stacking into suitable A-type Ising antiferromagnetic bilayers, the switchable out-of-plane ferroelectric polarizations through in-plane interlayer rigid sliding with low-power dissipation enable an effective tunability of the valley polarization and a further layer-locked anomalous valley Hall effect in a reversible and nonvolatile way. Once synthesized, these resultant room-temperature multiferroics could render energy-efficient and ground-breaking device applications in the post-Moore era for cutting-edge information processing and beyond. Finally, we elucidate the switchable valley physics by a simple perturbation theory.