title: Electric-Field Induced Activation of Dark Excitonic States in Carbon Nanotubes.
abstract: Electrical activation of optical transitions to parity-forbidden dark excitonic states in individual carbon nanotubes is reported. We examine electric-field effects on various excitonic states by simultaneously measuring photocurrent and photoluminescence. As the applied field increases, we observe an emergence of new absorption peaks in the excitation spectra. From the diameter dependence of the energy separation between the new peaks and the ground state of E11 excitons, we attribute the peaks to the dark excited states which became optically active due to the applied field. Field-induced exciton dissociation can explain the photocurrent threshold field, and the edge of the E11 continuum states has been identified by extrapolating to zero threshold.
authors.affiliation: Institute of Engineering Innovation, The University of Tokyo , Tokyo 113-8656, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Uda
authors.affiliation: Institute of Engineering Innovation, The University of Tokyo , Tokyo 113-8656, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Institute of Engineering Innovation, The University of Tokyo , Tokyo 113-8656, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ishii
authors.affiliation: Institute of Engineering Innovation, The University of Tokyo , Tokyo 113-8656, Japan.
authors.forename: Y K
authors.initials: YK
authors.lastname: Kato
keywords: Carbon nanotubes; dark excitons; exciton dissociation; field-effect transistors; photocurrent; photoluminescence