Switching ofK0.3MoO3at low temperatures. I. Response to the dc electric field

Electric-field-dependent nonlinear conductivity and the current response in the time domain for dc electric fields were investigated in ${\mathrm{K}}_{0.3}$ ${\mathrm{MoO}}_3$ at low temperatures, where a dramatic and sudden increase of the conductivity (we will refer to this increase as ‘‘switching’’) due to the collective contribution of the charge-density wave (CDW) was observed. The conductivity in the highly conducting state was found to increase with decreasing temperature, whereas the conductivity in the low-conducting state decreases with decreasing temperature. We interpret this phenomenon as a transition from the ordinary sliding state, which is already observed among various materials, to another sliding state with higher velocity, where the CDW can move without generating a backflow current of normal electrons. Around the threshold field for this switching, three kinds of current responses were observed in the time domain; these responses are likely to correspond to the three types of unit motions of the CDW. As a result of a detailed investigation of these responses, it is suggested that the current oscillation associated with the sliding motion of the CDW is usually generated in the bulk, but that the local mechanism for the generation of the oscillating current becomes dominant just around the switching threshold field. This implies that the amplitude mode should also be taken into account in order to obtain a correct description of the dynamics of the CDW.