Evaluation of superconducting gaps in optimally doped Ba(Fe1−xCox)2As2/Fe bilayers by ultrafast time-resolved spectroscopy

Measurements of nonequilibrium quasi-particle relaxation dynamics by using ultrafast pump and probe technique in optimally Co-doped Ba(Fe2As2)/Fe thin film has been reported. Multiple relaxation processes are present with BCS-like temperature-dependent superconducting gaps Δ0 = (3.67 ± 0.13) meV and Δ1 = (6.1 ± 0.1) meV, which are calculated considering the conventional electron-boson and spin fluctuations pairing mechanism. Then, the value of the electron-phonon coupling constant of λ = 0.18 has been obtained.