Point-contact study of ReFeAs(1-x)Fx (Re=La, Sm) superconducting films
arXiv:1103.3157 · doi:10.1088/0953-2048/24/6/065010
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 2Î\simeq 5-10 meV (for Re=Sm) with a maximum in the distribution around 6 meV. Temperature dependence of the gap Î(T) can be fitted well by BCS curve giving reduced gap ratio 2Î/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