Extended Data Fig. 2: Ultrafast nanobeam diffraction of CDW dynamics.

(a) Intensity of first-order NC (top) and IC (bottom) diffraction spots as a function of temporal delay for varying pump fluence. The data was recorded under tilted-sample conditions with an electron beam size of 170 nm and a repetition rate of 610 kHz. The NC curves are normalised as in Extended Data Fig. 1. We observe an initial suppression within 500 fs that scales with the pump fluence. Above a threshold of around 2 mJ/cm², the measured NC intensity after time zero equals the inelastically scattered background. For such higher fluences, we measure an increase of IC spot intensity within 5 ps with a temporal characteristic independent of the pump fluence. The IC curves are normalised to the corresponding NC curve intensities measured before time zero. (b) Delay scans of second-order NC intensity for varying pump fluence with the sample tilted into the zone-axis. In contrast to (a), the electron beam has a larger diameter (1.5μm), adding a spatiotemporal component to the dynamics following the initial suppression. For intermediate fluences, we witness a partial recovery of NC intensity after around 5 ps, followed by a second suppression at later delays. We attribute this behaviour to a global vibration of the specimen on the timescale of 500 ps and beyond, that modulates the detected intensity of diffraction spots in the ZOLZ as a result of the changing relative angle of incidence of the electron beam onto the sample. Furthermore, the locally varying excitation density leads to the formation and subsequent growth of IC phase domains on longer timescales (see Methods).