Complex low-frequency dielectric relaxation of the charge-density wave state in the (2.5(OCH3)(2)DCNQI)(2)Li

We report a detailed characterization of an unique 2- and 4-fold commensura te charge density wave (CDW) state. in single crystals of the organic condu ctor (2.5(OCH3)(2)DCNQI)(2)Li by means of low-frequency (0.1 Hz-1 MHz) diel ectric spectroscopy. We show that in addition to the narrow, Debye-like rel axation mode of strength Delta epsilon approximate to 10(7) with Arrhenius- like resistive decay, associated with long wavelength phason excitations, a new mode of weaker strength Delta epsilon approximate to 10(6) appears bel ow 40 K and broadens with decrease in temperature. Below 25 K the mean rela xation time of the new mode saturates, whereas the Debye mode continues, gr adual slowing down with weaker temperature dependence. again similar to the DC conductivity, We attribute the new process to short wavelength CDW exci tations that become dominant once the free carrier density is substantially reduced at low temperatures.