EFFECTS OF THE NONLINEAR ELECTRON-LATTICE INTERACTION ON THE ELECTRONIC STATES AND LOCALIZED MODES AROUND A SOLITON IN POLYACETYLENE

We have investigated the energy spectra, the electronic states and the localized modes of soliton by considering the effects of the square t erm of the electron-lattice interactions in the SSH model. Only the mi dgap state has been found, and the two bound states near the edge of t he valence band and the conduction band obtained in the standard SSH m odels, disappear. The energy gap and the dimerization increase, but th e total width of the energy band does not change. All five localized m odes survive, and their localizations are strengthened and the frequen cies are shifted.