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

Abstract

Phase slippage is required at the current electrodes of quasi-one-dimensional conductors with a charge density wave (CDW) ground state for the conversion from free to condensed carriers. We have performed at the ESRF high-resolution X-ray measurements of the spatially varying shift q( x) of the CDW satellite wave vector between current contacts on a thin NbSe 3 whisker in the sliding state. Applying direct currents, we observe at 90 K a steep exponential decrease of the shift within a few hundred microns from the contact. The CDW strain profile q( x) reflects the carrier conversion process, via nucleation and growth of phase-dislocation loops. Pulsed current measurements of the shift q show important differences between pulsed and dc current data, revealing a spatially dependent relaxational behaviour of the CDW strain. Using time-resolved high spatial resolution X-ray we observe at 300 μm from the electrode a stretched exponential-type decay of the shift q( t) upon switching off the current ( T=75 K) : q(t)=q 0[ exp(−t/τ) μ] with τ=23 ms and μ=0.36.