Fractional Charges and Frequency-Dependent Currents in Charge-Density-Wave Systems

It is shown that fractional charges of solitons in charge-density-wave systems can be measured directly by studying frequency-dependent currents. The nonlinear conductivity and the associated "noise" frequencies in Nb${\mathrm{Se}}_3$ are interpreted within this picture. Solitons with charge $e^{*}=\frac{e}{2}$ are expected. An analysis of existing experiments yields $e^{*}=0.3e-0.4e$.