Spectroscopic study of photoinduced charge-gap collapse in the correlated insulators Pr1-xCaxMnO3

We observed an instantaneous reflectance change triggered by pulse laser irradiation. The laser heating cannot account for the action spectra, which are indicative of the charge-gap collapse. It is found in Pr1-xCaxMnO3 for a wide range of Ca doping, x=0, 0.1, 0.2, 0.31, 0.4, and 0.5, which suggests that the photoinduced charge gap collapse is not characteristic of charge-ordered insulators. We propose that the photoinduced charge gap collapse can be a general behavior in strongly correlated insulators.