Single carbon nanotube photonics and the role of excitons

Abstract

Many-body effects in single-walled carbon nanotubes (SWNTs) were investigated using multi-color transient absorption spectroscopy. A population of excitons in isolated SWNTs was created by resonantly exciting the lowest allowed excitonic transition. With low pump fluence, photo-induced bleaching was observed regardless of the probe energy, as expected. However, at high pump fluence, photo-induced absorption was observed when probing at a higher energy than the pump. These observations are consistent with a blue-shifted exciton absorption due to phase-space filling effects at high exciton densities. As a result of the rapid loss of excited state population through Auger recombination, the blue shift recovered with a time constant of less than 1 ps.