Ultrafast Resonant Soft X-Ray Scattering in Manganites: Direct Measurement of Time-Dependent Orbital Order

We present ultrafast resonant soft-X-ray diffraction measurements of time-dependent orbital order in the single-layer-manganite La0.5Sr1.5MnO4. These experiments reveal the appearance of a metastable phase with reduced ordering, different from any thermal state of the system.