Kagome quantum anomalous Hall effect with high Chern number and large band gap

Zhen Zhang, Jing-Yang You,Xing-Yu Ma, Bo Gu, Gang Su

     Due to the potential applications in low-power-consumption spintronic devices, the quantum anomalous Hall effect (QAHE) has attracted tremendous attention in past decades. However, up to now, the QAHE was only observed experimentally in topological insulators with Chern numbers $C=1$ and 2 at very low temperatures. Here, we propose three two-dimensional stable kagome ferromagnets ${\mathrm{Co}}_3{\mathrm{Pb}}_3{S}_2,{\mathrm{Co}}_3{\mathrm{Pb}}_3{\mathrm{Se}}_2$, and ${\mathrm{Co}}_3{\mathrm{Sn}}_3{\mathrm{Se}}_2$ that can realize the QAHE with high Chern number of $\left|C\right|=3$. Monolayers ${\mathrm{Co}}_3{\mathrm{Pb}}_3{S}_2,{\mathrm{Co}}_3{\mathrm{Pb}}_3{\mathrm{Se}}_2$, and ${\mathrm{Co}}_3{\mathrm{Sn}}_3{\mathrm{Se}}_2$ possess the large band gap of 70, 77, and 63 meV with Curie temperature $T_C$ of 51, 42, and 46 K, respectively. By constructing a heterostructure Co₃Sn₃Se₂$/{\mathrm{MoS}}_2$, its $T_C$ is enhanced to 60 K and the band gap remains at about 60 meV due to the tensile strain of 2% at the interface. For the bilayer compound ${\mathrm{Co}}_6{\mathrm{Sn}}_5{\mathrm{Se}}_4$, it becomes a half metal, with a relatively flat plateau in its anomalous Hall conductivity corresponding to $\left|C\right|=3$ near the Fermi level. Our results provide topological nontrivial systems of kagome ferromagnetic monolayers and heterostructures possessing the QAHE with high Chern number $\left|C\right|=3$ and large band gaps.