Thermal hysteresis, threshold, and dynamics of charge-density waves at low temperaturesin blue bronzes s(A=Tl or Na)

The temperature dependence of Ohmic resistance, threshold, and nonlinear voltage-current (V-I) characteristics were systematically studied in pure potassium/thallium blue bronzes and Tl/Na-doped alloy bronzes. It is found that the thermal hysteresis of low-field resistance at a lower-temperature regime behaves quite differently as compared to that at higher temperatures; doping with metallic (Formula presented) /(Formula presented) ions has remarkable influences on the threshold electric-field properties of charge-density-wave (CDW) depinning, but has little effect on the low-temperature dynamics of CDW conduction below 30 K: the V-I characteristics in all samples still display a sharp breakdown transition. The results indicate that the low-temperature dynamical behavior of CDW depinning may not originate from the external impurities acting as weak pinning centers; rather, an internal mechanism concerning the changes of CDW structures in the presence of an applied electric field must be considered. The two different types of hysteresis behavior are strongly related to the correlation between the normal carriers and CDW configurations.