Density matrix renormalization group studies of low-dimensional magnetic systems and conjugated polymers

Abstract

To conclude, we have performed symmetrized DMRG calculations on the extended Hubbard–Peierls model. We have presented the dependences of exciton binding energy both on alternation ? and nearest-neighbor interaction parameter V. Our results provide reliable values for the ratio of Eb/E(1Bu) in PA and support the experimental findings that the exciton binding energy in PPV occurs in the weak-to-intermediate range (0.2–0.45 eV). Furthermore, the contradictory results that were present in the literature in the strong correlation limit have been clarified. Most interestingly, we have illustrated the counterintuitive result that the Hubbard U drastically reduces the 1Bu exciton binding energy. A simple perturbation plus SCI method has been employed to rationalize this result, though more rigorous physical explanations are required.