Phase slippage at the interface: normal metal/sliding charge-density wave

Phase slippage is required at the current electrodes of quasi-one-dimension al conductors with a charge density wave (CDW) ground state for the convers ion from free to condensed carriers. We have performed at the ESRF high-res olution X-ray measurements of the spatially varying shift q(x) of the CDW s atellite wave vector between current contacts on a thin NbSe3 whisker in th e sliding state. Applying direct currents, we observe at 90 K a steep expon ential decrease of the shift within a few hundred microns from the contact. The CDW strain profile q(x) reflects the carrier conversion process, via n ucleation and growth of phase-dislocation loops. Pulsed current measurement s of the shift q show important differences between pulsed and de current d ata, revealing a spatially dependent relaxational behaviour of the CDW stra in. Using time-resolved high spatial resolution X-ray we observe at 300 mu m from the electrode a stretched exponential-type decay of the shift q(t) u pon switching off the current (T = 75 K): q(t) = q(0)[exp( - t/tau)(mu)] wi th tau = 23 ms and mu = 0.36. (C) 2000 Elsevier Science B.V. All rights res erved.