Tunable correlated Chern insulators with giant magnetic anisotropy

Achieving a high-temperature quantum anomalous Hall (QAH) effect remains an experimental challenge despite extensive researches. One key limitation is the typically small magnetic anisotropy energy (MAE), generally ≤1 meV, which severely restricts stability of long-range magnetism in two-dimensional (2D) materials. In this work, we design a monolayer LiCoTe (with ferromagnetic T_C = 535 K) from first-principles calculations. A giant MAE value of 40.4 meV is observed for LiCoTe by applying 3.5% strain. A topological transition (from the half metal to the QAH state with Chern number C = -1) as well as a large global QAH band gap (up to 266 meV) is acquired under certain strain. Based on a tight-binding model, an orbital multiplet tuning mechanism involving d_xz/yz and d_x²-y² orbitals is proposed to rationalize the giant MAE and large QAH band gap. Our findings provide a promising pathway for achieving high-temperature 2D ferromagnets and Chern insulators in real correlated materials.