Extended Data Fig. 4: Capturing the picosecond strain reconfiguration in the FE phase and the formation of labyrinthine phase.

a. False color maps of scattering X-ray intensities include line profiles along q_z projection on the detector at a few representative values for incidence angle near the 002 Bragg diffraction condition. The comparison of the map collected before laser excitation and the corresponding map at 1 ps shows that the FE-phase peak position does not change on this timescale. On the other hand, the map recorded at 10 ps shows that the FE peak moved to substantially smaller q_z, which is consistent with a tetragonality increase in this region of the sample. At 10 ps, the satellites of FE vanished (not shown), and the “soup” emerged. The shifted superlattice peak shows that the polarization disorder persists throughout all layers of the superlattice. b. False color maps of detector images capturing the dynamics of diffuse scattering pattern near the 013 Bragg diffraction condition. Data is averaged over the marked time intervals to improve photon statistics of weak features in the pattern. The satellites along a streak corresponding to spatially modulated structure of V-phase is marked with a dashed rectangle. The dashed ellipsoid monitors the position of diffuse scattering of the L-phase, which develops after 10 ps.