1 research outputs found
Ultrafast Nanoimaging of the Photoinduced Phase Transition Dynamics in VO<sub>2</sub>
Many phase transitions in correlated
matter exhibit spatial inhomogeneities
with expected yet unexplored effects on the associated ultrafast dynamics.
Here we demonstrate the combination of ultrafast nondegenerate pump–probe
spectroscopy with far from equilibrium excitation, and scattering
scanning near-field optical microscopy (<i>s</i>-SNOM) for
ultrafast nanoimaging. In a femtosecond near-field near-IR (NIR) pump
and mid-IR (MIR) probe study, we investigate the photoinduced insulator-to-metal
(IMT) transition in nominally homogeneous VO<sub>2</sub> microcrystals.
With pump fluences as high as 5 mJ/cm<sup>2</sup>, we can reach three
distinct excitation regimes. We observe a spatial heterogeneity on
∼50–100 nm length scales in the fluence-dependent IMT
dynamics ranging from <100 fs to ∼1 ps. These results suggest
a high sensitivity of the IMT with respect to small local variations
in strain, doping, or defects that are difficult to discern microscopically.
We provide a perspective with the distinct requirements and considerations
of ultrafast spatiotemporal nanoimaging of phase transitions in quantum
materials