Re-integerization of fractional charges in the correlated quarter-filled band

Previous work has demonstrated the existence of soliton defect states with charges +/- e/2 in the limits of zero and of infinite on-site Coulomb interactions in the one-dimensional (1D) quarter-filled band. For large but finite on-site Coulomb interaction, the low temperature 2k_F bond distortion that occurs within the 4k_F bond-distorted phase is accompanied by charge-ordering on the sites. We show that a re-integerization'' of the defect charge occurs in this bond-charge density wave (BCDW) state due to a binding’’ of the fractional charges. We indicate briefly possible implications of this result for mechanisms of organic superconductivity.