Funct. Mater. 2025; 32 (3): 367-371.

The effect of high hydrostatic pressure on the fluctuation paraconductivity, Δσ(T), of the Y_0.66Pr_0.34Ba₂Cu₃O_7-δ single crystals has been studied. For all applied pressures, the experimental curves ρ(T) contain linear sections at temperatures T > T*. At temperatures T < T*, the ρ(T) curves deviate downwards from their linear extrapolation, i.e., excess conductivity Δσ(T) occurs in the studied samples. It is shown that the high hydrostatic pressure leads to the significant expansion of the temperature interval for the existence of excess conductivity, thereby narrowing the region of the ρ(T) linear dependence in the ab-plane in the normal state. The fluctuation conductivity is considered within the Lorentz-Doniach model. It was found that at pressures up to 9.7 kbar the value of the transverse coherence length χc(0) decreases from 5.47 to 5.06 &Angstrom;, simultaneously with an increase in T_c. Accordingly, the 2D-3D crossover temperature shifts toward higher values. This behavior is qualitatively different from similar baric dependences of χc(0), obtained both for pure YBaCuO samples of optimal composition and for single crystals lightly doped with praseodymium. Possible mechanisms of the influence of high pressure on the critical temperature and coherence length are discussed within framework of a model that assumes the presence of singularities in the charge carriers electron spectrum typical for lattices with strong coupling.