Coupling between single-particle and collective excitations in a charge-density-wave system: Field dependence of nonlinear conduction in the blue bronzeK0.3MoO3

We have investigated nonlinear characteristics of high-quality ${\mathrm{K}}_{0.3}$Mo${\mathrm{O}}_3$ single crystals in the temperature range of 30-100 K covering eight orders of magnitude in current and more than three decades in voltage. At some temperatures, high-field measurements were extended up to 1000 times the threshold electric field $E_T$ for nonlinear conduction. In the wide field and temperature range of the experiments, the charge-density-wave conductivity follows the empirical form ${\sigma }_{\mathrm{CDW}}\propto {\sigma }_n\left(\frac{E_T}{E}\right){(\frac{E}{E_T}-1)}^{\alpha }$, where ${\sigma }_n$ is the conductivity of normal carriers. Our results suggest that damping of the collective mode arises from dissipative normal currents induced by dynamic deformation of the charge-density wave.