(a) Time-resolved XRD spectra of GeTe after fs-laser irradiations. The black lines are the XRD spectra before excitation for comparing. The merging of (003) and (101) peaks indicate the symmetry transition from rhombohedral to cubic. (b) The Debye–Waller factor deduced from the intensity of electron diffraction as a function of laser fluence. By comparing with theoretical simulations, the change of intensities is also demonstrated to be an indication of the symmetry transition from rhombohedral to cubic. (c) The schematic illustration of Te-atom displacement model where the cubic symmetry is a direct result of Te-atom movement. (d) The schematic illustration of Ge-atom rattling model where the Ge atoms dynamically move around the center of cubic sites. The average effect leads to a signal of cubic symmetry. (e) The schematic illustration of randomly distributed long and short bonds. The diffraction signal of such a structure also shows a cubic symmetry. Panels (a) and (d) are reproduced from Ref. [42] with permission from the American Physical Society. Panels (b) and (c) are reproduced from Ref. [41] with permission from the American Chemical Society. Panel (e) is reproduced from Ref. [43] with permission from the American Chemical Society.