I will present some of the results obtained during my PhD thesis in the Quantum Photonics Group at ETH Zürich. We performed low-temperature, time-resolved optical spectroscopy on individual CoMoCat SWNTs immobilized on a functionalized substrate. We observed strongly localized emission and pronounced photon-antibunching, from which we deduce that photoluminescence originates from unintentional SWNT-quantum dots.
Moreover, the PL spectra are very broad and asymmetric, with a red-tail persisting down to 4 Kelvin. I will show how the spin-boson model can be used to account for the interaction between localized excitons and the 1-dimensional acoustical phonons in SWNTs. The model reproduces extremely well the PL line-shapes and their evolution with temperature. I will briefly mention potential consequences of this ultrafast pure-dephasing for quantum information applications.
Finally, I will describe a simple possible physical explanation for the strong exciton localization. Considering a single charge trapped in the close vicinity of the nanotube, we can show that it creates a confinement potential for the exciton in close agreement with most experimental features.