Localized excitons in 1D half-filled paramagnetic Hubbard model

By the example of the Hubbard model we analytically and numerically examine the formating and coexisting of localized electron–electron pairs (doublons) and localized electron–hole pairs (Frenkel–type excitons) . Here we demonstrate that at a variation of the on-site Coulomb repulsion U there occurs a quantum transition from the doublon to the exciton regime that is conditioned by the low-energy effective hybridization of the valence and conductivity subbands. We calculate momentum distribution functions and electronic spectrum functions for different U, which reveal topologically nontrivial behaviour at the Fermi level.