Fig. 3: Nanoscale X-ray spectroscopy of transient phases.
From: Ultrafast X-ray imaging of the light-induced phase transition in VO2
a, Frequency integrated hyperspectral CDI image at 20 ps pump–probe delay, showing clear topography but no signs of domains. b, Masks dividing the sample into regions that started in the R phase (red) and thus have not switched phase and in M1 phase (blue). c, Average transmission spectrum of blue and red regions at 20 ps delay. Shaded regions correspond to one standard deviation across all sample points. Also shown are calculated XAS spectra for a rutile metallic phase and an orthorhombically strained metallic phase (offset vertically). d, The measured difference in transmission (grey) between initially rutile and monoclinic regions (shaded regions correspond to one standard error) and the calculated value (black, offset vertically). e, Schematic evolution of the unit cell in VO2 following photoexcitation (not to scale). The system relaxes the vanadium dimers within the first 100 fs2, but cannot relax the strain on the same timescale. First the system is in a highly strained orthorhombic configuration, which preferentially relaxes along the out-of-plane direction (rutile b axis) within 20 ps, before relaxing the in-plane strain to give the rutile structure.
