We report transport measurements using pulsed magnetic fields to suppress the superconducting fluctuations (SCF) conductivity in a series of YBa_2Cu_3O_(6+x) samples. These experiments allow us altogether to measure the temperature T'c at which SCF disappear, and the pseudogap temperature T*. While the latter are consistent with previous determinations of T*, we find that T'c is slightly larger than similar data taken by Nernst measurements. A careful investigation near optimal doping shows that T* becomes smaller than T'c, which is an unambiguous evidence that the pseudogap cannot be assigned to preformed pairs. Studies of the incidence of disorder on both T'c and T* allow us to propose a phase diagram including disorder which explains most observations done in other cuprate families, and to discuss the available knowledge on the pseudogap line in the phase diagram.
@article{arxiv.1006.3165,
title = {Superconducting Fluctuations, Pseudogap and Phase Diagram in Cuprates},
author = {H. Alloul and F. Rullier-Albenque and B. Vignolle and D. Colson and A. Forget},
journal= {arXiv preprint arXiv:1006.3165},
year = {2010}
}