Effect of Long Aging on the Resistivity Properties of Optimally Doped Single Crystals

We investigate conducting properties in the basal abplane before and after a long time exposure in air atmosphere of optimally oxygen doped YBa₂Cu₃O_7-δ single crystals. Prolonged exposure leads to an increase of the effective scattering centers of the normal carriers. The excess conductivity in a wide temperature range has exponential temperature dependence and near the critical temperature is well described within the AslamazovLarkin theoretical model. The prolonged exposure increases to a great extent the temperature range of the implementation of the pseudogap state, narrowing the linear section of the temperature dependence of the resistivity in the ab-plane, ρ_ab(T).