title: Ultrafast spectroscopy of midinfrared internal exciton transitions in separated single-walled carbon nanotubes.
abstract: We report a femtosecond midinfrared study of the broadband low-energy response of individually separated (6,5) and (7,5) single-walled carbon nanotubes. Strong photoinduced absorption is observed around 200 meV, whose transition energy, oscillator strength, resonant chirality enhancement, and dynamics manifest the observation of quasi-one-dimensional intraexcitonic transitions. A model of the nanotube 1s-2p cross section agrees well with the signal amplitudes. Our study further reveals saturation of the photoinduced absorption with increasing phase-space filling of the correlated e-h pairs.
authors.affiliation: Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Jigang
authors.initials: J
authors.lastname: Wang
authors.forename: Matt W
authors.initials: MW
authors.lastname: Graham
authors.forename: Yingzhong
authors.initials: Y
authors.lastname: Ma
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kaindl