5d orbital Induced Room Temperature Quantum Anomalous Hall Effect in TbCl

Following the experimental realization of Quantum anomalous Hall (QAH) effect in thin films of chromium-doped (Bi,Sb)${}_2$Te${}_3$, enhancing the work temperature of QAH effect has emerged as a significant and challenging task. Here we demonstrate monolayer TbCl as a promising candidate to realize the room temperature QAH effect. Using DFT+U method, double checked by HSE06 and DMFT calculations, we identify the Hall conductivity $G=-e^2\mathrm{/}h$ per layer in three-dimensional ferromagnetic insulator TbCl, which is a weakly stacking of QAH layers. The monolayer TbCl inherits the magnetic and topological properties, exhibiting the QAH effect with Chern number $C$=-1. The large topological band gap reaches 42.8 meV, which is beyond room temperatue. The extended 5$d$ electrons lead to sizable exchange and superexchange interactions, resulting in a high Curie temperature $T_c$$\sim$457K. All these features demonstrate that monolayer TbCl will provide an ideal platform to realize the room temperature QAH effect.