Ultrafast photoexcited quasiparticle dynamics in YBCO films observed by THz emission
We observed a femtosecond time-transient nonequilibrium state in optically excited YBCO thin films for the first time. Ultrashort electromagnetic pulses were radiated from the films by an ultrafast supercurrent modulation with fs laser pulse irradiation. Quasiparticle dynamics was characterized by the analysis of the emission waveforms based on Rothwarf-Taylor rate equations.