Quantum anomalous Hall effect in two-dimensional Cu-dicyanobenzene coloring-triangle lattice

Magnetic two-dimensional (2D) topological insulators with spontaneous magnetization have been predicted to host quantum anomalous Hall effects (QAHEs). So far, most materials predicted for realizing the QAHE are inorganic. However, several theoretical works suggested the possibility of 2D organometallic frameworks as organic topological insulators (OTIs). For OTIs, the QAHE only exists in honeycomb or Kagome organometallic lattices. Recently, coloring-triangle (CT) lattice has been found to be mathematically equivalent to a Kagome lattice, suggesting a potential 2D lattice to realize QAHE. Here, based on first-principles calculations, we predict an organometallic CT lattice, Cu-dicyanobenzene (DCB), to be a stable QAH insulator. It exhibits ferromagnetic (FM) properties as a result of the charge transfer from metal atoms to DCB molecules. Moreover, based on the Ising model, the Curie temperature of the FM ordering is calculated to be around 100 K. Both the Chern numbers and the chiral edge states of the semi-infinite Cu-DCB edge structure, which occur inside the spin-orbit coupling band gap, confirm its nontrivial topological properties. These make the Cu-DCB CT lattice an ideal candidate to enrich the family of QAH insulators. [1]
[1]. Y. Gao et al., Nano Res. 13, 1571 (2020)