Electron irradiation and annealing effects on the pseudogap in optimally doped YBCO single crystals

摘要

The effect of room-temperature annealing on the basal-plane conductivity of YBCO single crystals is investigated after their irradiation with fast electrons. It is revealed that the excess conductivity Delta sigma(T) of the samples obeys an exponential temperature dependence in a broad temperature range T-f < T < T*. Here, Tf is the crossover temperature from the pseudogap to the fluctuation conductivity regime. The description of the excess conductivity with the expression Delta sigma proportional to T/T* exp(Delta*/T) can be interpreted in terms of the mean-field theory where T* corresponds to the mean-field transition temperature to the pseudogap state and the dependence Delta sigma(T) is described within the framework of the BCS-BEC crossover theory.