Matrix-product approach to conjugated polymers

The matrix product method (MPM) has been used in the past to generate varia tional Ansatze of the ground state (GS) of spin chains and ladders. In this paper we apply the MPM to study the GS of conjugated polymers in the valen ce bond basis, exploiting the charge and spin conservation as well, as the electron-hole and spin-parity symmetries. We employ the U-V-S Hamiltonian, which is a simplified version of the Pariser-Parr-Pople Hamiltonian. For se veral coupling constants U and V and dimerizations delta, we compute the GS energy per monomer, which agrees within a 2-4 % accuracy with the density- matrix renormalization group results. We also show the evolution of the MP- variational parameters in the weak and strong dimerization regimes.