Superconducting Order Parameter of the RbCa2Fe4As4F2 Compound

The superconducting order parameter of the RbCa 2 Fe 4 As 4 F 2 compound belonging to the new 12442 family of iron-based superconductors with a critical temperature of T c ~ 32 K has been studied. Two superconducting condensates with the order parameters Δ L ~ 6.3 meV and Δ S ~ 2.8 meV have been detected for the first time by multiple Andreev reflection spectroscopy. The temperature dependence of the superconducting critical current density J c ( T ) in the intrinsic field has been measured. The approximation of the dependence J c ( T ) demonstrates the correspondence of the experimental data to the double-gap model with the s -wave order parameter and the gaps of Δ L ~ 6 meV and Δ S ~ 2 meV. The superconducting order parameters obtained by two different methods are in good agreement with each other.