期刊
NANO LETTERS
卷 16, 期 5, 页码 3029-3035出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.5b05313
关键词
Nano-imaging; ultrafast spectroscopy; vanadium dioxide; s-SNOM; phase transition
类别
资金
- U.S. Department of Energy, Office of Basic Sciences, Division of Material Sciences and Engineering [DE-SC0008807]
- U.S. Department of Energy (DOE) [DE-SC0008807] Funding Source: U.S. Department of Energy (DOE)
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 (s-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 VO2 microcrystals. With pump fluences as high as 5 mJ/cm(2), we can reach three distinct excitation regimes. We observe a spatial heterogeneity on similar to 50-100 nm length scales in the fluence-dependent IMT dynamics ranging from <100 fs to similar 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.
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