VISUALIZATION OF THE LOCAL INSULATOR-METAL TRANSITION IN PR0.7CA0.3MNO3

The light-induced insulator-metal transition in the ''colossal magneto resistance'' compound Pr0.7Ca0.3MnO3 is shown to generate a well-local ized conducting path while the bulk of the sample remains insulating. The path can be visualized through a change of reflectivity that accom panies the phase transition. Its visibility provides a tool for gainin g insight into electronic transport in materials with strong magnetic correlations. For example, a conducting path can be generated or remov ed at an arbitrary position just because of the presence of another pa th. Such manipulation may be useful in the construction of optical swi tches.