Ultrafast Nanoimaging of the Photoinduced Phase Transition Dynamics in VO2

• DOI: 10.1021/acs.nanolett.5b05313
• Publication Date: 2016-04-20T19:42:44Z
• Authors: Sven A. Dönges; Omar Khatib; Brian T. O’Callahan; Joanna M. Atkin; Jae Hyung Park; David Cobden; Markus B. Raschke
• Keywords: Dynamics

Many phase transitions in correlated matter exhibit spatial inhomogeneities with expected yet unexplored effects on the associated ultrafast dynamics. Here we demonstrate combination of nondegenerate pump-probe spectroscopy far from equilibrium excitation, and scattering scanning near-field optical microscopy (s-SNOM) for nanoimaging. In a femtosecond near-IR (NIR) pump mid-IR (MIR) probe study, investigate photoinduced insulator-to-metal (IMT) transition nominally homogeneous VO2 microcrystals. With fluences as high 5 mJ/cm(2), can reach three distinct excitation regimes. We observe heterogeneity ∼50-100 nm length scales fluence-dependent IMT dynamics ranging <100 fs to ∼1 ps. These results suggest sensitivity respect small local variations strain, doping, or defects that are difficult discern microscopically. provide perspective requirements considerations spatiotemporal nanoimaging quantum materials.