Fully spin-polarized quadratic non-Dirac bands realized quantum anomalous Hall effect
The quantum anomalous Hall effect is a intriguing quantum state which exhibits the chiral edge states in the absence of magnetic field. While the search for quantum anomalous Hall insulators is still active, the researchers mainly search for the systems containing magnetic atom. Here, based on first-principles density functional theory, we predict a new family of Chern insulators with fully spin-polarized quadratic px,y non-Dirac bands in the alkali earth metal BaX (X = Si, Ge, Sn) system. We show that BaX monolayer has a half-metallic ferromagnetic ground state. The ferromagnetism is mainly originated from the p orbitals of Si, Ge and Sn atoms. The 2D BaSn monolayer exhibits a large magnetocrystalline anisotropic energy of 12.20 meV/cell and a nontrivial band gap of 159.10 meV. Interestingly, both the spin polarization of the chiral edge currents direction and the sign of Chern number can be tuned by doping. Furthermore, the 4% compressive strain can drive structural phase transition but the nontrivial topological properties remain reserve in the 2D BaX systems. Our findings not only extend the novel concepts but also provide fascinating opportunities for the realization of quantum anomalous Hall effect experimentally.