Ultrafast infrared nano-imaging of local electron-hole dynamics in CVD-grown single-walled carbon nanotubes.

Single-walled carbon nanotubes, as prototypical one-dimensional systems, have been extensively studied for their extreme confinement effects and the formation of strongly bound excitons. However, their high surface-to-volume ratio renders their dynamics highly susceptible to variations in the surrounding environment. Yet, visualizing photoinduced dynamics within individual nanotubes has remained a major challenge because of the lack of methods combining sufficient spatial and temporal resolution with sensitivity to an exceedingly small number of electron-hole pairs. Here, we apply ultrafast infrared nanospectroscopic imaging to probe local electron-hole dynamics in both isolated and bundled carbon nanotubes grown by chemical vapor deposition. This approach unravels heterogeneity in electron-hole pair creation and annihilation, arising from disordered stress within a tube and/or interactions with neighboring tubes. The capability to visualize local electron-hole dynamics in real time and space is essential for advancing carbon nanotubes as fundamental building blocks in nanophotonic and optoelectronic devices.