Stretched-Exponential Dielectric Relaxation in a Charge-Density-Wave System

The relaxation of the electric polarization is investigated in the charge-density-wave compound ${\mathrm{K}}_{0.3}$Mo${\mathrm{O}}_3$. Direct measurements of discharge current in the time interval of ${10}^{-5\mathrm{}}$ to ${10}^3$ s reveal a stretched exponential law for the time decay of polarization: $P=P_0\exp [-{\left\{\frac{t}{\tau }\mathrm{}\right(T\left)\right\}}^{1-n}]$, where both the initial polarization, $P_0$, and the exponent ($1-n=0.7$) are temperature independent. The time scale of the process indicates temperature activation with an activation energy equal to the single-particle Peierls gap. The glassy relaxation of randomly pinned charge-density waves is compared with recent theories and experiments on spin-glasses.