Vanishing of the upper critical field inBi2Sr2CaCu2O8+δfrom Landau-Ott scaling

Abstract

We apply Landau-Ott scaling to the reversible magnetization data of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ published by Wang et al. [Phys. Rev. Lett. 95, 247002 (2005)] and find that the extrapolation of the Landau-Ott upper critical field line vanishes at a critical temperature parameter ${T}_{c}^{*}$ a few degrees above the zero resistivity critical temperature ${T}_{c}$. Only isothermal curves below and near ${T}_{c}$ were used to determine this transition temperature. This temperature is associated with the disappearance of the mixed state instead of a complete suppression of superconductivity in the sample.