Spatiotemporal dynamics of excitons in isolated semiconducting single-walled carbon nanotubes are studied using transient absorption microscopy. Differential reflection and transmission of an 810-nm probe pulse after excitation by a 750-nm pump pulse are measured. We observe a biexponentially decaying signal with a fast time constant of 0.66 ps and a slower time constant of 2.8 ps. Both constants are independent of the pump fluence. By spatially and temporally resolving the differential reflection, we are able to observe a diffusion of excitons, and measure a diffusion coefficient of $200\pm 10$ cm${}^2/$s at room temperature and $300\pm 10$ cm${}^2$/s at lower temperatures of 10 K and 150 K.

• Received 16 August 2012

DOI:https://doi.org/10.1103/PhysRevB.86.205417