▎ 摘　　要

Monolayer graphene embedded with a transition metal nitride (i.e., XN4) has been experimentally synthesized recently, where a transition metal atom together with four nitrogen atoms as a unit are embedded in graphene to form a stable planar single-atom-thick structure. We provide a systematic study on the structural, electronic, and topological properties of these X N4-embedded graphene structures by utilizing both first-principles calculations and a tight-binding model. We find that X N4-embedded graphene (X = Pt, Ir, Rh, Os) can open topologically nontrivial band gaps that host two-dimensional Z2 topological insulators. We further show that the low-energy bands near the band gaps can be perfectly captured by a modified Kane-Mele model Hamiltonian. Our work not only provides concrete two-dimensional materials that are very rare to realize two-dimensional Z2 topological insulators, but also makes the graphene system to be realistic in hosting Kane-Mele type Z2 topological insulators.