Effects of pressure on the fluctuation conductivity of YBa/sub 2/Cu/sub 3/O/sub 7/

Abstract

The effects of hydrostatic pressure up to 1.11 GPa on the in-plane fluctuation conductivity of YBa2Cu3O7−d are investigated. The experiments are focused on the asymptotic region closely above Tc where a threedimensional Gaussian and genuine critical regimes are identified. From the analysis of the Gaussian critical amplitude one deduces that the off-plane coherence length E(0) does not change significantly with pressure in the studied range. At low applied pressures the asymptotic critical exponent indicates the occurrence of a scaling beyond three-dimensional XY. However, at the highest studied pressure, this exponent assumes a value consistent with the predictions of the full-dynamic three-dimensional XY universality class. The width of the critical regime, as measured by the Ginzburg criterium, increases significantly with pressure. This result is related to a pressure-induced reduction of the in-plane coherence length Eab(0).