Ultrafast Polaron Dynamics in La(0.7)Ca(0.3)MnO(3) Thin Films

Abstract

In this work, we use ultrafast optical pump-optical probe (OPOP) spectroscopy to probe the polaron dynamics in La(0.7)Ca(0.3)MnO(3) (LCMO) thin films. The temporal evolution in transient reflectivity change Delta R/R exhibits two relaxing components: a fast component with a time constant of subpicosecond and a slow component with time constant ranging from tens of ps to hundreds of ps. The amplitude of the fast component exhibits the similar temperature depence with that of the resistivity, and the neutron scattering intensity due to nanoscale correlated polarons. The results strongly suggest that the fast photoinduced reflectivity change may have been due to the photoexcitation and trapping process of correlated Jahn-Teller (T-J) polarons in the paramagnetic (PM) and ferromagnetic (FM) phases.