Topological half-metallic features in alkali metal doped CrCl3 monolayers

Two-dimensional (2D) topological half metals, namely, empowering nontrivial topological states with 100% spin-polarized 2D systems, may find important applications in low-dissipation spintronics. However, exploration of such intriguing materials is still very challenging. The recently discovered 2D magnetic materials provide unprecedented opportunities to realize 2D topological half-metallic state. Using first-principles calculations, we first find that the ferromagnetism of $\mathrm{Cr}{\mathrm{Cl}}_{3}$ monolayer can be well reserved by doping alkali metals, in fact, whose Curie temperature can be enhanced from 23 to 66 K after doping K. Then, we notice that semiconducting to Dirac half-metallic phase transition is achieved via Na and K doping, where the linear Dirac dispersion originates from the honeycomb lattice formed by Cr atoms. Most strikingly, Na- and K doped $\mathrm{Cr}{\mathrm{Cl}}_{3}$ exhibit quantum anomalous Hall effect (QAHE) with Chern number $C=1$, while the Li-doped one harbors high Chern number QAHE with $C=\ensuremath{-}2$. Thus, our work provides a theoretical guideline to realize 2D topological half-metallic state, rendering it as a promising platform for future applications.