Correlation Effects on the Phonons Localized around a Soliton or a Polaron in Polyacetylene

Abstract

Structures of phonon modes are investigated, when there is a charged soliton, a spin soliton or a polaron in trans-polyacetylene. Electron correlations are considered in the form of the on-site and nearest-neighbor Coulomb repulsions, in addition to the electron-phonon Hamiltonian by Su, Schrieffer and Heeger. The Hartree-Fock approximation is used. All the localized phonons, previously found in the SSH model, survive the electron correlations so far as the ground states are in the bond order wavestate. Their frequencies are shifted by the correlations. In most cases, the shift by the on-site repulsion is in the opposite direction to that by the nearest-neighbor repulsion. A charged soliton gives the frequency shifts which are in the opposite direction to those by a spin soliton.