Intrinsic Dirac half-metal and quantum anomalous Hall phase in a hexagonal metal-oxide lattice

Abstract

The quantum anomalous Hall (QAH) effect has attracted extensive attention due to time-reversal symmetry broken by a staggered magnetic flux emerging from ferromagnetic ordering and spin-orbit coupling. However, the experimental observations of the QAH effect are still challenging due to its small nontrivial bulk gap. Here, based on density functional theory and Berry curvature calculations, we propose the realization of intrinsic QAH effect in two-dimensional hexagonal metal-oxide lattice, $\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{3}$, which is characterized by the nonzero Chern number $(C=1)$ and chiral edge states. Spin-polarized calculations indicate that it exhibits a Dirac half-metal feature with temperature as large as ${T}_{C}=392\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ using spin-wave theory. When the spin-orbit coupling is switched on, $\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{3}$ becomes a QAH insulator. Notably, the nontrivial topology is robust against biaxial strain with its band gap reaching up to ${E}_{g}=75\phantom{\rule{0.16em}{0ex}}\mathrm{meV}$, which is far beyond room temperature. A tight-binding model is further constructed to understand the origin of nontrivially electronic properties. Our findings on the Dirac half-metal and room-temperature QAH effect in the $\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{3}$ lattice can serve as an ideal platform for developing future topotronics devices.