Time-resolved (a) imaginary part of the dielectric function and (b) XRD intensity of GST after the fs laser irradiation. The intensity of the dielectric function dramatically decreases and then recovers to a certain degree which seems to be a behavior of electrons. In contrast, the intensity of XRD decreases slowly but remains stable which is regarded as the change of structures. (c) Schematic illustrations of the excitation-induced intermediate phase by structural rotation. Panels (a) and (b) are reproduced from Ref. [35] with permission from the Nature Publishing Group. Panel (c) is reproduced from Ref. [36] with permission from the Nature Publishing Group under a Creative Commons Attribution 4.0 International License (CC BY 4.0).