Influence of Uniform Compression on the Temperature Dependence of the Pseudogap of Medium-Praseodymium-Doped Y1−xPrxBa2Cu3O7−δ Single Crystals

The effect of high pressure on the conductivity in the basal plane of HTSC single crystals of Y0.77Pr0.23Ba2Cu3O7−δ is investigated. It has been established that the excess conductivity, Δσ(T), of these single crystals in a wide temperature range Tf < T < T* can be described by an exponential temperature dependence. The description of the excess conductivity using the relation Δσ ~ (1 − T/T*)exp(Δ*ab/T) can be interpreted in terms of the mean-field theory, where T* is represented as the temperature pseudogap opening, and the temperature dependence of the pseudogap (PG) is satisfactorily described in the framework of the BCS-BEC crossover theory. An increase in the applied pressure leads to the effect of narrowing the temperature interval for the realization of the PG-regime, thereby expanding the region of the linear dependence ρ(T) in the ab-plane.

EVOLUTION OF OVER-CONDUCTIVITY OF YВа2Сu3О7-δ SINGLE CRYSTALS UNDER THE EXPOSURE OF IRRADIATION BY HIGH-ENERGY ELECTRONS

The evolution of the excess conductivity of YВа2Сu3О7-δ single crystals upon electron irradiation is investigated. It was shown that electron irradiation leads to a significant expansion of the temperature range for the existence of excess conductivity, thereby narrowing the region of the linear dependence of ρ(Т) in the ab plane. It was found that the excess conductivity ∆σ(Т) of YВа2Сu3О7-δ single crystals in a wide temperature range Tf<Т<T* (Тf – the transition temperature from the PG to the FP mode) is subject to exponential temperature dependence. Moreover, the description of excess conductivity using the relation ∆σ ~ (1-Т/Т*)exp( ∆*ab/T) (Δ*ab – the pseudogap in ab-plane) can be interpreted in terms of the mean-field theory, where T* is presented as the mean-field temperature of the transition to the PG state, and the temperature dependence of the pseudogap is satisfactorily described in the framework of the BCS-BEC crossover theory. In this case, the value of the transverse coherence length ξс(0) increases 1.4 times and the 2D-3D crossover point shifts in temperature.