Manipulation of the valley degree of freedom provides a novel paradigm in quantum information technology. In this work, through first principles calculations, we demonstrate that monolayer $\mathrm{Gd}{\mathrm{I}}_2$ is a promising candidate material for valleytronic applications. Monolayer $\mathrm{Gd}{\mathrm{I}}_2$ can be easily exfoliated from bulk, and it is spontaneously valley polarized with a giant splitting of 149 meV due to its intrinsic ferromagnetism and large spin orbital coupling. The anomalous valley Hall effect could be realized in monolayer $\mathrm{Gd}{\mathrm{I}}_2$ by an appropriate external electric field. Furthermore, the valley polarization feature is stable against the biaxial in-plane strain. Our findings provide an extraordinary and potential material platform for experimental studies and practical applications in the emergent field of valleytronics.

• Received 29 December 2020
• Accepted 10 February 2021

DOI:https://doi.org/10.1103/PhysRevB.103.125121