CHARGE FLUCTUATIONS IN ONE-DIMENSIONAL QUARTER-FILLED SPIN-DENSITY-WAVE STATES WITH DIMERIZATION

The charge fluctuation of the SDW (spin density wave) state has been e xamined for a system which consists of one-dimensional quarter-filled band with repulsive interactions of both on-site and nearest-neighbor site (U and V) and the dimerization energy ltd). The commensurability energy in the ground state is studied within the mean-field theory and the collective mode representing the charge fluctuation is calculated in terms of the random phase approximation. It is found that the gap of the excitation spectrum, omega g, induced by the commensurability e nergy vanishes at a critical value of V corresponding to the onset of the coexistence of 2k(F)-SDW and 4k(F)-CDW (charge density wave) where k(F) denotes the Fermi wave number. The spectral weight indicates the enhancement of the charge fluctuation in the presence of the energy V which competes with energies t(d) and U.