An exact diagonalization approach to the electronic structure of quasi-one-dimensional systems

An exact diagonalization approach is developed to solve the extended Hubbard model in momentum space, aiming to investigate the electronic and optical properties of quasi-one-dimensional systems. By taking only a small number of k-points, with appropriate parameterization, our method is able to capture the low-energy excitation spectra of graphene nanoribbons, reproduce the essential features of the GW-BSE calculations, and give rise to a result closely aligned with the experiment.