Vanishing of the upper critical field in Bi_2Sr_2CaCu_2O_{8+\delta} from Landau-Ott scaling

TL;DR

This study uses Landau-Ott scaling on magnetization data of Bi-2212 to identify a critical temperature where the mixed state vanishes, which is slightly above the zero resistivity T_c, indicating a transition related to the disappearance of the mixed state.

Contribution

It applies Landau-Ott scaling to existing magnetization data to pinpoint a critical temperature associated with the vanishing of the mixed state in Bi-2212.

Findings

The upper critical field line vanishes at T*_c, above T_c.

T*_c is linked to the disappearance of the mixed state.

The transition is observed through isothermal curves near T_c.

Abstract

We apply Landau-Ott scaling to the reversible magnetization data of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ published by Y. Wang et al. [\emph{Phys. Rev. Lett. \textbf{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 to T_c were used to determine this transition temperature. This temperature is associated to the disappearance of the mixed state instead of a complete suppression of superconductivity in the sample.