We explore the internal structure and the relative coherence of sliding charge-density-wave (CDW) domains in switching crystals of pure and iron-doped ${\mathrm{NbSe}}_3$. CDW domain coherence is examined by studying the current-voltage (I-V) characteristics when a temperature gradient is applied across a switching sample. We use a noninvasive voltage-probe technique to further determine the structure of switching domains. We find that drastically different results are obtained depending on the unperturbed nature of a sample’s I-V characteristic, and suggest that this large variation in switching crystal I-V characteristics originates from differences in the distribution of the switch-causing ultrastrong impurities. These results are discussed in terms of a phase-slip model of switching.

• Received 9 October 1987

DOI:https://doi.org/10.1103/PhysRevB.37.8817