Comment on 'Diamagnetism and Cooper pairing above Tc in cuprates'

TL;DR

This paper demonstrates that the magnetization behavior observed above Tc in optimally doped YBa2Cu3O7-d can be explained by the Gaussian-Ginzburg-Landau approach, challenging claims of phase-disordering mechanisms.

Contribution

It shows that mean-field Ginzburg-Landau theory adequately describes the magnetization data above Tc, countering previous interpretations of phase-disordering.

Findings

Magnetization above Tc explained by GGL approach

Challenges phase-disordering interpretation

Supports earlier lower-field measurements

Abstract

It is shown that the magnetization rounding measured by L. Li and coworkers above the superconducting transition in optimally doped YBa2Cu3O7-d crystals under magnetic fields up to 14 T [Phys. Rev. B 81, 054510 (2010), arXiv:0906.1823] may be explained at a phenomenological level in terms of the mean field Gaussian-Ginzburg-Landau (GGL) approach for layered superconductors. This result challenges the claims of L. Li and coworkers, who write '[...] we are observing the phase-disordering mechanism, rather than Gaussian mean-field fluctuations', but it is in full agreement with earlier magnetization measurements by different authors in optimally-doped YBa2Cu3O7-d under lower magnetic fields. The adequacy of the mean-field Ginzburg-Landau descriptions is further confirmed when analyzing in terms of the GL scaling in the lowest-Landau-level (GL-LLL) approximation the magnetization data reported below Tc by L. Li and coworkers.