Pressure effect on the electrical resistance of Y0.77Pr0.23Ba2Cu3O7-δ single crystals

Abstract

The effect of hydrostatic pressure up to 12 kbar on the electrical resistance in the basal ab-plane of optimally oxygen-doped (δ<0.1) single crystals Y_1–xPr_xBa₂Cu₃O_7–δ moderately doped with praseodymium (x≈0.23) with a critical temperature T_c≈67 K. Compared to undoped single-crystal YBa₂Cu₃O_7–δ, doping with praseodymium led to a decrease in the critical temperature by ≈24 K with a simultaneous increase in ρ_ab (300 K) by ≈130 μΩcm. In the region of the transition to the superconducting state, several clearly pronounced peaks are observed on the dρ/dT – T curves, which indicates the presence of several phases with different critical temperatures in the sample. The application of high hydrostatic pressure leads to an increase in T_c by about 3 K. This increase slows down with increasing pressure, and the baric derivatives, dT_c/dP, decrease from 0.44 K/kbar at atmospheric pressure to 0.14 K/kbar at 11 kbar. The comparatively weak change in the critical temperature under the action of hydrostatic pressure is due to the relatively small value of the orthorhombic distortion, (a–b)/a. The change in the baric derivative dT_c/dP upon all-round compression of the sample is due to the fact that, along with an increase in the Debye temperature, the matrix element of the electron-phonon interaction also increases. Possible mechanisms of the effect of high pressure on T_c are discussed taking into account the presence of features in the electronic spectrum of carriers.