Critical fields and fluctuations determined from specific heat and magnetoresistance in the same nanogram SmFeAs(O,F) single crystal

TL;DR

This study compares specific heat and magnetoresistance measurements in a single crystal of SmFeAs(O,F) to analyze superconducting fluctuations, revealing discrepancies with theoretical models and validating a method for estimating Hc2 slope.

Contribution

It provides a direct comparison of fluctuation effects from two measurement techniques in the same crystal, highlighting limitations of existing models for this material.

Findings

Superconducting fluctuations scale within the 2D-LLL scheme but do not match the 3D nature of the material.

Specific heat transition cannot be fully described by LLL or XY scaling.

The fluctuation analysis method yields consistent Hc2 slope estimates.

Abstract

Through a direct comparison of specific heat and magneto-resistance we critically asses the nature of superconducting fluctuations in the same nano-gram crystal of SmFeAs(O, F). We show that although the superconducting fluctuation contribution to conductivity scales well within the 2D-LLL scheme its predictions contrast the inherently 3D nature of SmFeAs(O, F) in the vicinity T_{c}. Furthermore the transition seen in specific heat cannot be satisfactory described either by the LLL or the XY scaling. Additionally we have validated, through comparing Hc2 values obtained from the entropy conservation construction (Hab=-19.5 T/K and Hab=-2.9 T/K), the analysis of fluctuation contribution to conductivity as a reasonable method for estimating the Hc2 slope.