Özet:

The e ect of high hydrostatic pressures of up to 10 kbar on the basal ab-plane conductivity of YBa2Cu3O7−δ single crystals with unidirectional twin boundaries is investigated. We show that application of a high pressure leads to a substantial decrease of the pressure derivative of the coherence length dξc/dP while increasing dTc/dP and a temperature shift of the 2D-3D crossover point. Possible mechanisms of the influence of high pressure on the critical temperature and the coherence length are discussed within the frames of a model assuming the presence of singularities in the charge carriers electron spectrum typical for lattices with strong coupling. The excess conductivity Δσ (T) in YBa2Cu3O7−δ has been revealed to obey an exponential dependence in the wide temperature range Tc

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