High-performance quantum anomalous Hall effect in monolayer Ti2Sb2KRb and Ti2Bi2NaK

Quantum anomalous Hall (QAH) insulators are an ideal platform for developing topological electronic devices, but their low observation temperature limits the applications. In this study, based on first-principles calculations, monolayer Ti2Sb2KRb and Ti2Bi2NaK are demonstrated to be QAH insulators with topological gaps 43 and 57 meV, respectively. Their Chern numbers are calculated to be C=-2. The study of electronic structures indicates that the ferromagnetic topological property is induced by the energy band inversion of dxy and dx2-y2 orbitals for Ti atoms near the Dirac cone. Both monolayer Ti2Sb2KRb and Ti2Bi2NaK exhibit a perpendicular magnetic anisotropy, and their Curie temperatures are estimated to be 480 and 478 K, respectively. The ferromagnetic coupling is induced by the small crystal-field splitting energy caused by Sb and Bi atom's large radius. Our study suggests that monolayer Ti2Sb2KRb and Ti2Bi2NaK are promising candidates for room temperature QAH insulators.