Magnetization-induced phase transition from a semimetal to a Chern insulator in monolayer VGa2Te4

Quantum anomalous Hall (QAH) insulators host many exotic topological properties including the gapped bulk states and the dissipationless chiral edge states, which have both fundamental scientific importance and the potential application in future electronic devices. Inspired by the ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ (MBT) family, we design a new class of compounds $X{Z}_{2}{T}_{4}$ ($X=\mathrm{V}$, Mn, Ni; $Z=\mathrm{Ga}$, In; $T=\mathrm{Se}$, Te) by substituting Bi of group VA with $Z$ of group IIIA. Based on density functional theory calculations, we find that the $Z$ atoms favor the $Z{T}_{4}$ tetrahedra in $X{Z}_{2}{T}_{4}$ rather than the ${\mathrm{BiTe}}_{6}$-like octahedral geometry in MBT. After investigating the magnetic and electronic structures of 36 materials in the $X{Z}_{2}{T}_{4}$ family, we pick out the $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{VGa}}_{2}{\mathrm{Te}}_{4}$ monolayer with tunable topological properties, which can transit from a trivial gapless ferromagnetic semimetal into a QAH insulator with a 10-meV global band gap. Our studies on $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{VGa}}_{2}{\mathrm{Te}}_{4}$ provide a practical example to explore more QAH insulators beyond the MBT family.