Two-dimensional intrinsic ferrovalley Janus 2H-VSeS monolayer with high Curie temperature and robust valley polarization

Inspired by the unique physical properties of two-dimensional (2D) V-based Janus dichloride monolayers with intrinsic ferromagnetism and high Curie temperature ${T}_{c}$, we investigate the electronic structure, spin-valley polarization, and magnetic anisotropy of a Janus 2H-VSeS monolayer in detail using first-principles calculations. The results show that the Janus 2H-VSeS monolayer exhibits a large valley polarization of 105 meV, high ${T}_{c}$ of 278 K, and in-plane magnetocrystalline anisotropy contributed by the ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}/{d}_{xy}$ orbitals of V atoms. The biaxial strain ($\ensuremath{-}8%<\ensuremath{\varepsilon}<8%$) can effectively tune the magnetic moments of the V atom, valley polarization $\mathrm{\ensuremath{\Delta}}E, {T}_{c}$, and magnetocrystalline anisotropy energy of the Janus 2H-VSeS monolayer. The corresponding $\mathrm{\ensuremath{\Delta}}E$ and ${T}_{c}$ are adjusted from 72 to 106.8 meV and from 180 to 340 K, respectively. Due to the broken space- and time-reversal symmetries, opposite valley charge carriers carry opposite Berry curvatures, which leads to prominent anomalous Hall conductivity at the $K$ and ${K}^{\ensuremath{'}}$ valleys. The maximum modulation of Berry curvature can reach to 45% and 9.5% by applying the biaxial strain and charge carrier doping, respectively. The stable in-plane magnetocrystalline anisotropy and robust spontaneous valley polarization make the ferromagnetic Janus 2H-VSeS monolayer a promising material for achieving spintronic and valleytronic devices.