Point-contact study of ReFeAs(1-x)Fx (Re=La, Sm) superconducting films

Abstract

Point-contact (PC) Andreev-reflection (AR) measurements of the superconducting gap in iron-oxipnictide ReFeAsO_{1-x}F_x (Re=La, Sm) films have been carried out. The value of the gap is distributed in the range 2Δ\simeq 5-10 meV (for Re=Sm) with a maximum in the distribution around 6 meV. Temperature dependence of the gap Δ(T) can be fitted well by BCS curve giving reduced gap ratio 2Δ/kT_c^*\simeq 3.5 (here T_c^* is the critical temperature from the BCS fit). At the same time, an expected second larger gap feature was difficult to resolve distinctly on the AR spectra making determination reliability of the second gap detection questionable. Possible reasons for this and the origin of other features like clear-cut asymmetry in the AR spectra and current regime in PCs are discussed.

6 two-column pages, 6 figs., 26 Refs., to be published in Superconductor Science and Technology

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• Lessons from Oxypnictide Thin Films
• The superconducting gaps in FeSe studied by soft point-contact Andreev reflection spectroscopy
• Exploring of point-contact spectra of Ba1-xNaxFe2As2 in the normal and superconducting state
• Point contact spectroscopy in Fe-based superconductors: recent advancements and future challenges
• Differential conductance of point contacts between an iron-based superconductor and a normal metal