Evaluation of superconducting gaps in optimally doped Ba(Fe sub(1-) sub(x)Co sub(x)) sub(2)As sub(2)/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(Fe sub(2)As sub(2))/Fe thin film has been reported. Multiple relaxation processes are present with BCS-like temperature-dependent superconducting gaps Delta sub(0) = (3.67 plus or minus 0.13) meV and Delta sub(1) = (6.1 plus or minus 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 lambda = 0.18 has been obtained.