ELECTRON INTERACTION AND SOLITON ENERGY IN CONJUGATED POLYMER

The effect of e-e interaction on the creation energy of soliton in pol ymer has been extensively studied by using the Hubbard model. However, the polymer possesses wide bandwidth, which is even larger than the o n-site repulsion U, then it can't be guaranteed that the Hubbard model is always suitable, since this model originates from the systems with narrow band. Actually the Hubbard model only contains the diagonal pa rt of e-e interaction, for wide band system, the off-diagonal part of e-e interaction may have substantial impact. This paper goes beyond th e Hubbard model by using a screened Coulomb interaction, which include s both diagonal and off-diagonal parts. Our calculation shows that the effect of e-e interaction on the creation energy of soliton is distin ctly different from the result based on the Hubbard model, the physica l reason cause this difference is analysed.