Defects and charge density waves in irradiated layer and chain compounds

Abstract

Controlling the defect concentration by irradiation permits detailed investigations of the effects of defects on the charge density wave phenomena. With experiments on irradiated layer and chain compounds we have characterised these effects. The electronic transport properties, the phase transition temperatures and the structural coherence of the charge density waves have been followed as a function of the concentration of irradiation induced defects from the ppm level up to 10⁻² atomic fraction. The pinning by defects affects the dynamic properties of the charge density wave already at defect concentrations of the ppm level. At higher defect concentrations of the level of 10⁻³ atomic fraction, the pinned charge density wave becomes strongly strained. Its structural coherence breaks down and a concomitant decrease of the critical temperature of the charge density wave transition is observed.