Low-frequency dielectric spectroscopy of commensurate density waves

We overview complex conductivity measurements (20Hz - 1MHz) in low-dimensio nal organic systems kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, and deuterated Cu-DC NQI and its alloys, with commensurate density wave ground states. We discus s the obtained results in comparison with those for the incommensurate dens ity waves, like in (TMTSF)(2)PF6, in which the phason relaxation in a disor dered background dominates. We show that in the commensurate systems with a random domain structure charged domain walls provide a more appropriate de scription of the observed dielectric relaxation.