Superconducting Order Parameter of the RbCa₂Fe₄As₄F₂ Compound

The superconducting order parameter of the RbCa₂Fe₄As₄F₂ 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.