A study of the superconducting order parameter is conducted using multiple Andreev reflection spectroscopy and an analysis of the critical current density behavior in the intrinsic field of a polycrystalline sample of DyFeAsO0.88F0.12 (Tc = 42 K) in the temperature range from 1.54 K to Tc. The critical current density temperature dependence in the two-zone case were derived within the framework of the Bardeen–Cooper–Schriffer (BCS) model. It has been demonstrated that, in the case of double-gap superconductivity, experimental data are closely aligned with theoretical predictions. The values of the superconducting gaps as determined by approximations are in good agreement with those defined through the analysis of Andreev reflection spectra.
Danyarkhodzhaev et al. (Sun,) studied this question.