Effect of electron irradiation on the pseudogap temperature dependence of YBa $$_2$$ 2 Cu $$_3$$ 3 O $$_{7-\delta }$$ 7 - δ single crystals

Abstract

The effect of electron irradiation on the basal-plane conductivity $$\sigma (T)$$ of YBa $$_2$$ Cu $$_3$$ O $$_{7-\delta }$$ single crystals is investigated. The excess conductivity $$\Delta \sigma (T)$$ has been revealed to obey an exponential temperature dependence in the broad temperature range $$T_f< T < T^*$$ , where $$T_f$$ is the transition temperature from the pseudogap state to the regime of fluctuation conductivity. The description of the excess conductivity by the relation $$\Delta \sigma (T) \propto (1-T/T^*)\exp (\Delta ^*_{ab}/T)$$ can be interpreted in terms of the mean-field theory where $$T^*$$ is the mean-field transition temperature to the pseudogap state and $$\Delta ^*(T)$$ is satisfactory described within the framework of the BCS-BEC crossover theory. In all, electron irradiation of the YBa $$_2$$ Cu $$_3$$ O $$_{7-\delta }$$ single crystals has been revealed to lead to an expansion of the temperature range of the pseudogap state, thereby narrowing the range of the linear dependence of $$\rho (T)$$ in the ab-plane.