Engineering Dirac cones and topological flat bands with organic molecules

Abstract

We investigated polyhedral \ensuremath{\pi}-conjugated molecules with threefold rotation symmetry, which can be suitable building blocks for both Dirac cones and a topological flat-band system. The two dimensional network structures of such molecules can be characterized by intra- and intermolecular interactions. We constructed tight binding models of these structures by systematically changing the intra- $({t}_{0})$ and intermolecular $({t}_{1})$ transfer integrals as independent parameters. The degree of freedom for the interactions provides a topological flat band and a massless or massive Dirac cone. We analyzed the topological features and origins of the flat band and Dirac cone of a molecule-based triangular lattice.