Time-dependent strandlike domains in the charge-density-wave states of NbSe3: An effect not induced by electric field

We have made observations of the strandlike domains associated with the charge-density-wave phase transitions in Nb${\mathrm{Se}}_3$ with electric fields applied along the $b$ axis of the crystal. No electric-field—induced changes of the strandlike domains were observed suggesting that the time-dependent images observed in Nb${\mathrm{Se}}_3$ by dark-field electron microscopy [K. K. Fung and J. W. Steeds, Phys. Rev. Lett. 45, 1696 (1980)] do not originate from the depinning of charge-density waves by electric fields. We note that the time-dependent images are found only in a minority of the samples that we have examined. The origin of the strandlike domains and its time-dependent effect in Nb${\mathrm{Se}}_3$ remains obscure at present despite our thorough understanding of the domain structures of incommensurate charge-density waves in other systems such as $2H-\mathrm{T}\mathrm{a}{\mathrm{Se}}_2$.