Vortex transport entropy in the H-T diagram of high Tc superconductors

The combination of Nernst effect and electrical resistivity measurements allows to extract the transport entropy carried by moving vortices. In high Tc superconductors, the vortex-like fluctuations close and above Tc can be detected with these tools if local phase coherence is still present. In this work we study the vortex transport entropy in the two milestone high Tc, YBa2Cu3O7-δ (YBCO) and Bi2Sr2CaCu2O8+δ (BSCCO). While below Tc the YBCO entropy displays a mean field like behavior, close and above Tc the entropy reveals typical features of strong superconducting fluctuations. The lower dimensionality in BSCCO enhances the strength of superconducting fluctuations in a wider region of the H - Tdiagram and a mean field treatment can not be applied. In this region the vortex transport entropy remains unaffected by the presence of correlated defects.