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
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.
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2011