Action spectra of the two-stage photoinduced insulator-metal transition in Pr1-xCaxMnO3

The action spectra for the photoinduced insulator-metal transition in Pr1-xCaxMnO3 were investigated in the 0.45-3.05 eV range. The photon-density threshold for the transition exhibits a gaplike behavior at similar to 0.4 eV with anisotropic features, and it is insensitive to the degree of carrier doping x. A two-stage mechanism is proposed for the transition. In the first stage, photoexcited charge carriers melt down the charge-ordered state by screening effects, which is followed by a local formation of metastable metallic domains. In the second stage, the barrier between the metallic domains is overcome by an applied electric field resulting in a continuous conducting path that remains stable as long as the current is maintained. [S0163-1829(99)03935-1].