Quantum spin Hall and Z2 metallic states in an organic material

Motivated by recently searching for topological states in organic materials as well as successful experimental synthesis of a graphitelike metal-organic framework Ni3(C18H12N6)2 [Sheberla, J. Am. Chem. Soc. 136, 8859 (2014)JACSAT0002-786310.1021/ja502765n], we systematically investigated the electronic and topological properties of the Ni3(C18H12N6)2 monolayer using an ab initio method combined with a tight-binding model. Our calculations demonstrate that the material can be in a quantum spin Hall or Z2 metallic state in different electron-doped concentrations, which are experimentally accessible with currently electrostatic gating technologies. The tight-binding model also shows that the real next-nearest-neighbor interaction is essential to drive the Z2 metallic phase in Ni3(C18H12N6)2-type lattices.