title: High energetic excitons in carbon nanotubes directly probe charge-carriers.
abstract: Theory predicts peculiar features for excited-state dynamics in one dimension (1D) that are difficult to be observed experimentally. Single-walled carbon nanotubes (SWNTs) are an excellent approximation to 1D quantum confinement, due to their very high aspect ratio and low density of defects. Here we use ultrafast optical spectroscopy to probe photogenerated charge-carriers in (6,5) semiconducting SWNTs. We identify the transient energy shift of the highly polarizable S33 transition as a sensitive fingerprint of charge-carriers in SWNTs. By measuring the coherent phonon amplitude profile we obtain a precise estimate of the Stark-shift and discuss the binding energy of the S33 excitonic transition. From this, we infer that charge-carriers are formed instantaneously (<50 fs) even upon pumping the first exciton, S11. The decay of the photogenerated charge-carrier population is well described by a model for geminate recombination in 1D.
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Soavi
authors.affiliation: 1] Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy [2] IFN-CNR, Piazza L. da Vinci, 32, 20133 Milano, Italy [3] Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli, 70/3, 20133 Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Scotognella
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Viola
authors.affiliation: Inst. for Physical and Theoretical Chemistry Dept. of Chemistry and Pharmacy, University of Wuerzburg, Wuerzburg 97074, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Hefner
authors.affiliation: Inst. for Physical and Theoretical Chemistry Dept. of Chemistry and Pharmacy, University of Wuerzburg, Wuerzburg 97074, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Hertel
authors.affiliation: 1] Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy [2] IFN-CNR, Piazza L. da Vinci, 32, 20133 Milano, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.affiliation: 1] Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy [2] Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli, 70/3, 20133 Milano, Italy.
authors.forename: Guglielmo
authors.initials: G
authors.lastname: Lanzani