Femtosecond pump-probe studies showed that carrier dynamics in MgB2 films were governed by the sub-ps electron-phonon (e-ph) relaxation present at all temperatures, the few-ps e-ph process well pronounced below 70K, and the sub-ns superconducting relaxation below TC. The amplitude of the superconducting component versus temperature followed the superposition of the isotropic dirty gap and the 3-dimensional π gap dependences, closing at 2 different TC values. The time-constant of the few-ps relaxation exhibited a double divergence at temperatures corresponding to the TC values of the 2 gaps.

Time-Resolved Photoexcitation of the Superconducting Two-Gap State in MgB2 Thin Films. Y.Xu, M.Khafizov, L.Satrapinsky, P.Kus, A.Plecenik, R.Sobolewski: Physical Review Letters, 2003, 91[19], 197004 (3pp)