H. Requardt

X-ray scattering evidence for macroscopic strong pinning centers in the sliding CDW state of NbSe3

Using high-resolution X-ray scattering techniques, we measure the variation, q(x), of the position in reciprocal space of the CDW satellite, in the sliding state, along the length of NbSe3 whiskers. We show that structural defects and intentionally X-ray radiation-damaged regions increase locally the CDW pinning force, and induce CDW phase distortions which are consistent with those observed near contacts. Using the semi-microscopic model in Ref. [1] describing the normal ↔ condensed carrier conversion, with spatially varying parameters, we account for the experimental spatial dependence of the CDW phase gradient near both types of defects. PACS numbers: 71.45.Lr, 72.15.Nj, 61.10−i

High resolution X-ray scattering techniques for studying the sliding CDWS distortions, in NbSe3

Abstract The phase gradient in a sliding-charge density wave (CDW), which is observable as a longitudinal shift, q ∝∂ φ /∂ x , of the CDW satellite peak position, is due to the conversion free-electrons↔CDW-condensate, at the current electrodes. Using high resolution X-ray scattering techniques and time-resolved techniques, we monitor, on thin NbSe 3 whiskers, the shift, q ( x ), and its relaxation, q ( t ), upon switching off the current.

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

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 prole q(x )r e#ects the carrier conversion process, via nucleation and growth of phase-dislocation loops. Pulsed current measurements of the shift q show important di!erences 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 lm from the electrode a stretched exponential-type decay of the shift q(t) upon switching o! the current („75 K): q(t)q 0 [exp(!t/q)k] with q23 ms and k0.36. ( 2000 Elsevier Science B.V. All rights reserved.