The observation of the characteristic Kosterlitz-Thouless behavior requires the attaintment of the two dimensional limit where the correlation-length anisotropy, gamma=gsiab/gsic, diverges. Our findings strongly suggest that the failure of several experiments on films and single crystals to observe any trace of KT-behavior is attributable either to inhomogeneities or doping by means of chemical substitution.
@article{arxiv.cond-mat/0610230,
title = {On the occurrence of Kosterlitz-Thouless behavior in cuprate superconductors},
author = {T. Schneider},
journal= {arXiv preprint arXiv:cond-mat/0610230},
year = {2007}
}