INFLUENCE OF ELECTRON IRRADIATION DEFECTS ON THE TRANSPORT PROPERTIES OF CUPRATES

Abstract

We use electron irradiation at low temperature to introduce defects in a controlled manner in the cuprates. We have shown in YBCO 7 that the main influence on transport properties is due to stable defects in the CuO 2 plane. They are found analogous to Zn substitution on the copper planar site.1 Compared to impurity substitutions, the great advantage of electron irradiation is to allow to study the physical properties of a single sample with an increasing defect content. Tc and electrical resistivity measurements have been performed on electron irradiated single crystals of different cuprates (YBCO, Bi-2212, Hg-1223, T1-2201) for a wide range of hole dopings nh. A simple correlation between the decrease of Tc and the increase of residual resistivity ΔR2D is found, as expected for d ware superconductivity. The ratio ΔTc/ΔR2D, which is expected to be proportional to nh/m* is found to reproduce the variation of nh from the under-doped to the over-doped regime.2 This demonstrates that the hole content is the relevant parameter to describe the transport properties all over the phase diagram. For large defect contents, low T upturns of the resistivity are observed in under-doped YBCO 6.6 and over-doped T1-2201 (see Ref. [3]). In the highly over-doped T1 compound the decrease of conductivity scales as expected from weak localization theory. For YBCO 6.6 the large low T contribution to the resistivity is shown to be initially proportional to the defect content. It might therefore be associated to Kondo like spin flip scattering term. This would be consistent with the results on the magnetic properties induced by spinless defects such as Li (see Ref. [4]).