Engineering a two-dimensional kagome topological insulator from porous graphene

Our study sets forth a carbon-based two-dimensional (2D) kagome topological insulator without containing any metal atoms that aligns the Fermi level with the Dirac point without the need for doping, overcoming a significant bottleneck issue observed in 2D metal-organic framework-based kagome structures. Our 2D kagome structure, formed by creating patterned nano pores in the graphene sheet, nomenclatured as porous graphene-based kagome lattice (PGKL), is inspired by the recent bottom-up synthesis of similar structures. Because of the absence of mirror symmetry in our porous graphene, by considering only the first nearest neighbor intrinsic spin-orbit coupling (ISOC) within the tight-binding model, unlike the mostly used next nearest neighbor ISOC in the Kane-Mele model for graphene, PGKL exhibits distinctive band structures with Dirac bands amidst flatbands, allowing for the realization of topological states near the Fermi level. Delving into Berry curvature and Chern numbers provides a comprehensive understanding of the topological insulating properties of PGKL, offering valuable insights into 2D topological insulators. Analysis of the 1D ribbon structure underscores the emergence of topological edge states.