Carrier dynamics in EuTiO$_{3}$ films probed by femtosecond pump-probe spectroscopy*

Recently, perovskite oxide EuTiO$_{3}$ has attracted considerable attention due to its intriguing multiferroic properties. To gain a deeper understanding of its fascinating properties, it is essential to characterize the competing interactions between charge, lattice, spin, and orbital parameters. Here we present optical studies of the ultrafast carrier dynamics in EuTiO$_{3}$ films grown on SrTiO$_{3}$ substrates by probing photo-induced transient absorption (TA) in the weak excitation limit. All the signals were measured at room temperature. The transient curve of EuTiO$_{3}$ exhibits a fast rise after photo excitation (approximately 2 ps) and a long decay component with time constant of several nanoseconds, which are attributed to carrier-phonon coupling and carrier recombination respectively. The absorption change of EuTiO$_{3}$ near zero temporal delay is found to be quite different from the SrTiO$_{3}$ substrates, implying carrier-phonon interactions differ distinctively between these two materials. Our results could be helpful to understand the microscopic interactions in perovskite oxide.