Ultrafast Dynamics in Optimally Doped YBa_2Cu_3O_(7-δ) Observed with White Light Pump-probe Spectroscopy

摘要

The quasiparticle relaxation dynamics in optimally doped (001) YBa_2Cu_3O_(7-δ) thin films were measured at various temperatures by white light pump-probe technique. The 2D ultrafast spectroscopy with broadband (～200 nm) and high time-resolution (～9 fs) was performed by the non-collinear optical parametric amplifier (NOPA). The relaxation time and the amplitude of the transient transmissivity changes (ΔT/T) are wavelength-dependent. The maximum ΔT/T appears at around 625 nm (～1.98 eV) which corresponds to the transition between the Fermi level and the UHB (upper Hubbard band). Furthermore, the oscillations with ～150, ～320, ～500 cm~(-1) have been clearly observed in the Fourier transformed graph of the 2D ultrafast spectroscopy, which are consistent with the phonon modes in Raman-scattering spectra.