Optoacoustical spectrum of the metal-insulator transition compound NdNiO3: Sub-picosecond pump-probe study

A pump-probe optical spectroscopy technique was used to study the time-resolved reflectivity ΔR(t)/R in the range 0-160 ps of the metal-insulator transition compound NdNiO3. It enables, for the first time, the direct real-time observation of the non-equilibrium electron dynamics in the insulating and in the metallic state of that compound and the acoustical response. Strong change of the transient reflectivity is observed as a function of temperature. First of all, the magnitude of the fast component of transient reflectivity ({ΔR(t)/R}max, 0-3 ps) increases drastically when T