Topological Haldane Insulator in a Graphene Nanoribbon Superlattice.

Besides the well-classified single-particle topological phases, the discovery of electron-electron interaction-induced many-body topological phases in realistic materials has inspired great research interest. In this work, based on first-principles, density matrix renormalization group, and exact diagonalization calculations, we investigate the long-range Coulomb interaction-driven topological phases in the experimentally synthesized one-dimensional (1D) graphene nanoribbon superlattice (GNRS). Based on entanglement spectra and edge spin excitations, the topological phase diagram is mapped out in the interaction parameter space, forming two distinctive topological Haldane insulator (THI) phases and one charge density wave phase. The first-principles-derived interaction parameters place 1D GNRS in one THI phase with edge spin-1/2 slightly moved away from the outermost lattice site, which is distinguishable from the conventional THI phase through scanning tunneling microscopy-based electron-spin resonance measurements. Our results demonstrate the formation of correlated topological phases in 1D GNRS that are accessible by current experimental techniques.