Abundant valley-polarized states in two-dimensional ferromagnetic van der Waals heterostructures
Huisheng Zhang, Wenjia Yang, Yaohui Ning, Xiaohong Xu
Abstract
Manipulating the valley degree of freedom provides a novel paradigm for future valleytronics. Here we use first-principles approaches and the $kp$ model analyses to carry out a comparative study of ten van der Waals (vdW) heterostructures constructed by transition-metal dichalcogenides and recently discovered two-dimensional (2D) ferromagnetic (FM) insulators. Our calculations show that the $\mathrm{MoT}{\mathrm{e}}_{2}/\mathrm{CrB}{\mathrm{r}}_{3}$ heterostructure hosts a large valley splitting of $\ensuremath{\sim}28.7\phantom{\rule{0.16em}{0ex}}\mathrm{meV}$, which is much larger than that observed in the $\mathrm{WS}{\mathrm{e}}_{2}/\mathrm{Cr}{\mathrm{I}}_{3}$ heterostructure $(\ensuremath{\sim}3.5\phantom{\rule{0.16em}{0ex}}\mathrm{meV})$. Specifically, the spin-orbital coupling can induce band inversions in $\mathrm{WS}{\mathrm{e}}_{2}/\mathrm{CrB}{\mathrm{r}}_{3}$ and $\mathrm{MoT}{\mathrm{e}}_{2}/\mathrm{CrB}{\mathrm{r}}_{3}$ heterostructures due to strong charge transfer across the interfaces of these two systems. Most strikingly, $\mathrm{WS}{\mathrm{e}}_{2}/\mathrm{CrB}{\mathrm{r}}_{3}$ is characterized as a valley-polarized quantum anomalous Hall effect system with Chern number $C=\ensuremath{-}1$ at the $K$ point while $C=0$ at the ${K}^{\ensuremath{'}}$ point. All those findings together with recent progress in 2D FM insulators point out an experimentally achievable scheme for exploration of abundant valley-polarized states in 2D FM vdW heterostructures.