Prediction of two-dimensional Dirac materials with intrinsic magnetism, quantum anomalous Hall effect and high Curie temperature

Abstract

The intrinsic functionality of two-dimensional (2D) materials is crucial for both fundamental studies and practical applications in information processing and storage. In particular, 2D ferromagnets have emerged as a major research field, bringing in new concepts, physical effects, and device designs. More competitive ferromagnetic materials in 2D systems with the quantum anomalous Hall (QAH) state and room-temperature ferromagnetism are much desired. Herein, we predicted stable XC₆ (X = V, Nb, and Cu) monolayers through first-principles calculations. Novel topological properties, including the gapless edge state, anomalous hall conductance, Chern number and Berry curvature, were systematically investigated. Without spin–orbit coupling, both VC₆ and NbC₆ monolayers are ferromagnetic Dirac half-metals, while CuC₆ monolayers is a nonmagnetic Dirac semimetal. With spin–orbit coupling, both VC₆ and NbC₆ monolayers exhibit intrinsic QAH insulators with large out-of-plane magnetocrystalline anisotropy energy and a high Curie temperature of 425 K and 520 K, respectively, and the CuC₆ monolayer is a quantum spin Hall (QSH) insulator. Our results provide a promising platform for realizing the QAH and QSH phases and the fantastic integration of Dirac physics, spintronics, and valleytronics.