Pressure effects on the fluctuation conductivity of YBCO

We perform in-plane resistivity measurements under hydrostatic pressures up to 1.11 GPa on a YBCO single crystal. Fluctuation contributions to the conductivity are studied. When the temperature approaches T-c from above, we first observe a regime dominated by 3D Gaussian fluctuations which are robust against the pressure in the studied range. With decreasing temperatures a crossover occurs at a temperature T-G to a behavior described by critical fluctuations. The so-called Ginzburg temperature, T-G, as well as the Ginzburg number, increase under pressure. We also observe an internal structure of the critical region, which evolves upon the application of pressure. (C) 2004 Elsevier B.V. All rights reserved.