The temperature and field dependence of reversible magnetization have been measured on a YBa2Cu3O7−δ single crystal at six different doping concentrations. It is found that the data above 2 T can be described by the scaling law based on the GL-LLL (lowest Landau level approach based on Ginzburg-Landau theory) critical fluctuation theory yielding the values of the slope of upper critical field −dHc2(T)/dT near Tc. This set of values is self-consistent with that obtained in doing the universal scaling for the six samples. Based on a simple Ginzburg-Landau approach, we determined the doping dependence of the coherence length ξ which behaves in a similar way as that determined from ξ=ℏvF/Esc with Esc the superconducting energy scale. Our results may suggest a growing coherence length towards more underdoping.
@article{arxiv.cond-mat/0603781,
title = {Reversible magnetization and critical fluctuations in systematically doped YBa$_2$Cu$_3$O$_{7-\delta}$ single crystals},
author = {Hong Gao and Cong Ren and Lei Shan and Yue Wang and Yingzi Zhang and Shiping Zhao and Xin Yao and Hai-Hu Wen},
journal= {arXiv preprint arXiv:cond-mat/0603781},
year = {2009}
}