VX2 (X = S, Se, Te) monolayers: Intrinsic quantum anomalous Hall insulator with high Curie temperature and large gap

Abstract

Two-dimensional (2D) magnetic materials have flourished to date, with ferromagnetic (FM) materials providing a broad platform for exploring the novel quantum anomalous Hall (QAH) effect. However, the extremely low working temperature in most QAH candidates significantly limits the experimental realization. Herein, we designed a series of transition metal chalcogenide VX2 (X = S, Se, Te) monolayers using first-principles calculations and investigated their electronic and topological properties. The results indicate that all these materials are dynamically stable FM 2D materials. Notably, VTe2 is identified as an intrinsic room-temperature QAH insulator with the Chern number of C = 1 and a sizable bandgap of 0.14 eV. This large bandgap arises from the band inversion between the spin-up bands contributed by the px and py orbitals of Te atoms. Additionally, VTe2 exhibits a Curie temperature of 444 K, exceeding the room temperature. VS2 and VSe2 monolayers are FM semiconductors whose electronic properties can be turned by applying external strains. Among them, the VSe2 monolayer becomes a QAH insulator with C = 1 under suitable biaxial compressive strains. This study introduces a category of QAH candidates that show significant promise for implementation in spintronic devices.