Temperature Dependence of the Macroscopic Superconducting Order Parameter in Ba0.45K0.55Fe₂As₂

Single crystals of the overdoped iron pnictide Ba 0.45 K 0.55 Fe ₂ As ₂ with Tc≈ 29 K have been studied. The current–voltage characteristics of planar mechanically controlled break junctions at various temperatures have been obtained and analysed. The temperature dependence of the self-field bulk critical supercurrent in zero magnetic field is successfully described within a two-band model, which made it possible to estimate the values of the large and small superconducting gaps, their characteristic ratios, and the partial contributions of the two effective bands to the conductivity.