Full analytical solution of finite-length armchair/zigzag nanoribbons

Finite-length armchair graphene nanoribbons can behave as one-dimensional topological materials, that may show edge states in their zigzag-terminated edges, depending on their width and termination. We show here a full solution of tight-binding graphene rectangles of any length and width that can be seen as either finite -length armchair or zigzag ribbons. We find exact analytical expressions for both bulk and edge eigenstates and eigenenergies. We write down exact expressions for the Coulomb interactions among edge states and introduce a Hubbard-dimer model to analyze the emergence and features of different magnetic states at the edges, whose existence depends on the ribbon length. We find ample room for experimental testing of our predictions in N = 5 armchair ribbons. We compare the analytical results with ab initio simulations to benchmark the quality of the dimer model and to set its parameters. A further detailed analysis of the ab initio Hamiltonian allows us to identify those variations of the tight-binding parameters that affect the topological properties of the ribbons.

Automated summary

Finite-length armchair graphene nanoribbons can exhibit one-dimensional topological properties with edge states, depending on their width and termination. We provide a complete solution for tight-binding graphene rectangles of any length and width, which can be seen as either finite-length armchair or zigzag ribbons. We derive exact expressions for the bulk and edge eigenstates and eigenenergies. We also investigate the Coulomb interactions among edge states and analyze the emergence and characteristics of different magnetic states at the edges using a Hubbard-dimer model.