THERMAL HYSTERESIS, THRESHOLD, AND DYNAMICS OF CHARGE-DENSITY WAVES AT LOW-TEMPERATURES IN BLUE BRONZES (K(1-X)A(X))(0.3)MOO3 (A=TL OR NA)

The temperature dependence of Ohmic resistance, threshold, and nonline ar voltage-current (V-I) characteristics were systematically studied i n pure potassium/thallium blue bronzes and Tl/Na-doped alloy bronzes. It is found that the thermal hysteresis of low-field resistance at a l ower-temperature regime behaves quite differently as compared to that at higher temperatures; doping with metallic Tl+/Na+ ions has remarkab le influences on the threshold electric-held properties of charge-dens ity-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 indic ate that the low-temperature dynamical behavior of CDW depinning may n ot originate from the external impurities acting as weak pinning cente rs; rather, an internal mechanism concerning the changes of CDW struct ures 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.