Excess conductivity and pseudo-gap state in YBCO single crystals slightly doped with Al and Pr

Abstract

In this work we investigate the conductivity in the base plane of YBa2Cu3O7 (YBCO) single crystals with slight (up to 5%) aluminium (Al) and praseodymium (Pr) doping and with a given topology of plane defects. The results indicate that the doping with Al and Pr results to the increase of the number of the effective scattering centers of the normal carriers. The excess conductivity for the analyzed single crystals, within a wide temperature interval, is described by an exponential temperature dependence. Near the critical temperature (T c) it is well approximated by the Aslamazov–Larkin theoretical model. A small doping with Pr enhances a significant narrowing regarding the temperature interval in which the pseudo-gap (PG) is realised. On the contrary, the Al doping with the same concentration results to the expansion of the temperature interval of excess conductivity existence.