LOW-FREQUENCY DIELECTRIC RESPONSE OF CHARGE-DENSITY-WAVE PINNED BY COMMENSURABILITY IN (2,5(OCH3)(2)DCNQI)(2)LI

We have used complex conductivity measurements between 20 Hz and 1 MHz to probe the dielectric response in the low-temperature phase of the (2, 5(OCH3)(2)DCNQI)(2)Li organic conductor. The observed data reveal the existence of the relaxation process which is well described by a D ebye-like expression for an overdamped response of a system with a sin gle degree of freedom. Both the static dielectric constant (epsilon(0) = 3 x 10(7)) and the characteristic relaxation time (tau(0)) are much larger than that expected for single-particle excitations. tau(0) is thermally activated in a manner similar to the de conductivity. We att ribute the observed relaxation to N = 4 charge density wave pinned by commensurability to the underlying lattice.