Two-dimensional topological insulators with binary honeycomb lattices : SiC₃ siligraphene and its analogs

Silicon carbide and other group-IV binary materials with 1:1 stoichiometry are trivial semiconductors. Using first-principles calculations combined with a tight-binding model, we demonstrate two-dimensional (2D) silicon carbide materials (siligraphenes) with 1:3 and 3:1 stoichiometries are topological insulators (TIs) superior to graphene. Dirac cones and topologically nontrivial electronic structures are predicted in these binary honeycomb lattices. The band gaps opened at the Dirac points due to the spin-orbital coupling (SOC) are several orders of magnitude larger than the graphene value. Such interesting properties also exist in their analogs of other group-IV elements, such as g-GeC₃, g-Ge₃C, g-GeSi₃, and g-Ge₃Si. The TI states predicted in these unique lattices broaden the application field of group-IV binary materials and open the door to searching for 2D TIs with enhanced SOC.