Slow dynamics of the photoinduced phase transition in Pd(dmit)₂ salts (dmit = 1,3-dithiol-2-thione-4,5-dithiolate)

Slow dynamics of the initially photoinduced state has been observed by the pump-probe type time-resolved reflection spectroscopy in the charge separated phase of the half-filled strong dimer system, Et₂Me ₂Sb[Pd(dmit)₂]₂ (dmit = 1,3-dithiol-2-thione-4, 5-dithiolate). We have succeeded to reproduce the probe photon energy dependence of the time profile qualitatively in the time delay range from 10 ps to 1 ns assuming the dynamical expansion of the domain of the photo-induced dimer-Mott insulating phase in the host charge-separated one.