LATTICE VIBRATION SPECTRA IN ONE-DIMENSIONAL CONDUCTORS

For one-dimensional conductors with half- filled band, the lattice vibration spectra, both acoustic and optical branches, are obtained analytically in the dimerized state. It is shown that, there exist not only a gap in k=π/2 Brillouin zone boundary,but also a gap between the optical and acoustic phonon branches when the electron-lattice coupling cons- taut λ is Larger than λ_c(=0.21). Then,the frequency of the Staggered mode around solitons can be described analytically for any coupling constant λ.