Strain-induced tunable valley polarization and topological phase transition in SVSiN₂ monolayer

The potential application of a two-dimensional (2D) ferrovalley semiconductor in the field of valleytronics has sparked extensive research interest. Using first-principles calculations, we predict that the SVSiN2 monolayer is a promising ferrovalley material with excellent dynamical and thermal stability, and its Curie temperature is around room temperature. A giant valley polarization of -72.73 meV is obtained by shifting the magnetization direction from in-plane to out-of-plane. The valley-contrasting properties of the SVSiN2 monolayer can be remarkably modulated by in-plane strains. Most importantly, topological phase transition is predicted to be realized by a 5.5-6% tensile strain, which is verified by the nonzero Chern number and the nontrivial edge state. Compared to the in-plane strain modulation, the valley-dependent properties of the SVSiN2 monolayer are robust to vertical electric fields. Our findings could enrich the physical understanding of the effects of manipulating the valley-dependent properties of 2D ferrovalley semiconductors, facilitating potential applications of 2D Janus monolayers for valleytronics.