Eur. Phys. J. B 83, 423-428 (2011)
https://doi.org/10.1140/epjb/e2011-20527-9

Regular Article

Study of the in-plane and c-axis fluctuation conductivity of melt-textured YBa₂Cu₃O₇ under hydrostatic pressure

¹ Departamento de Física, Universidade Federal de Pelotas, P.O. Box 354, 96010-900 Pelotas, RS, Brazil
² Instituto de Física, Universidade Federal do Rio Grande do Sul, P.O. Box 115051, 91501-970 Porto Alegre, RS, Brazil
³ Departamento de Física, Pontifícia Universidade Catílica do Rio de Janeiro, 22453-900, Rio de Janeiro, RJ, Brazil
⁴ Departamento de Física, Universidade Estadual de Ponta Grossa, 84031-510 Ponta Grossa, PR, Brazil
⁵ Institut de Ciència de Materials de Barcelona, CSIC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

^a e-mail: ppureur@if.ufrgs.br

Received: 30 June 2011
Received in final form: 30 August 2011
Published online: 24 October 2011

Abstract

We have experimentally studied the pressure dependence of the fluctuation conductivity in melt-processed YBa₂Cu₃O₇ (YBCO) for currents applied parallel or perpendicular to the Cu-O₂ atomic layers. Results show that the asymptotic critical regime is described by the 3D-XY universality class for both in-plane and off-plane conductivity components. The dynamical exponent for the in-plane conductivity component is z = 1.5, independently of the applied pressure. However, a pressure induced crossover in the dynamical universality class is observed in the c-axis fluctuation conductivity, where the exponent changes gradually from z = 1.5 to z = 2. The Ginzburg number increases with pressure for both crystalline orientations. This behavior suggests that the in-plane and c-axis components of the G-L coherence length decrease upon pressure application. The fluctuation spectrum for the Gaussian regime in the planar conductivity keeps the three dimensional character. However, filamentary fluctuations are observed along the c-axis above the Ginzburg temperature. Our results for the out-of-plane fluctuation conductivity in YBCO suggest that the c-axis transport is predominantly coherent in this system.