Phase-coherence effects in vortex transport entropy

BRIDOUX G.; NIEVA G.; DE LA CRUZ F.

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Año: 2008 vol. 101 p. 1 - 4

0031-9007

Nernst and electrical resistivity measurements in superconducting YBa2Cu3O7-d and Bi2Sr2CaCu2O8+d with and without columnar defects show a distinctive thermodynamics of the respective liquid vortex matter. At a field-dependent high temperature region in the H-T phase diagram, the Nernst signal is independent of structural defects in both materials. At lower temperatures, in YBa2Cu3O7-d, defects contribute only to the vortex mobility, and the transport entropy is that of a system of vortex lines. The transition to lower temperatures in Bi2Sr2CaCu2O8+d has a different origin; the maximum in the Nernst signal when decreasing temperature is not associated with transport properties but with the entropy behavior of pancake vortices in the presence of structural defects.