Fractionally Charged Excitations in Charge-Density-Wave Systems with Commensurability 3

A theoretical study of topological excitations (kinks) in a one-dimensional one-third-filled Peierls system is presented. The charges associated with the kinks are found to be fractional $Q=\pm \frac{1}{3}e,\pm \frac{2}{3}e$. Calculations of the spatial widths and electronic structure of different types of kinks are carried out numerically. Possible applications to tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) are mentioned.