title: Nonlinear photoluminescence spectroscopy of carbon nanotubes with localized exciton states.
abstract: We report distinctive nonlinear behavior of photoluminescence (PL) intensities from localized exciton states embedded in single-walled carbon nanotubes (SWNTs) at room temperature. We found that PL from the local states exhibits strong nonlinear behavior with increasing continuous-wave excitation power density, whereas free exciton PL shows only weak sublinear behavior. The strong nonlinear behavior was observed regardless of the origin of the local states and found to be nearly independent of the local state density. These results indicate that the strong PL nonlinearity arises from a universal mechanism to SWNTs with sparse local states. The significant nonlinear PL is attributed to rapid ground-state depletion of the local states caused by an efficient accumulation of photogenerated free excitons into the sparse local states through one-dimensional diffusional migration of excitons along the nanotube axis; this mechanism is verified by Monte Carlo simulations of exciton diffusion dynamics.
authors.affiliation: Institute of Advanced Energy, Kyoto University , Uji, Kyoto 611-0011, Japan.
authors.forename: Munechiyo
authors.initials: M
authors.lastname: Iwamura
authors.forename: Naoto
authors.initials: N
authors.lastname: Akizuki
authors.forename: Yuhei
authors.initials: Y
authors.lastname: Miyauchi
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Mouri
authors.forename: Jonah
authors.initials: J
authors.lastname: Shaver
authors.forename: Zhenghong
authors.initials: Z
authors.lastname: Gao
authors.forename: Laurent
authors.initials: L
authors.lastname: Cognet
authors.forename: Brahim
authors.initials: B
authors.lastname: Lounis
authors.forename: Kazunari
authors.initials: K
authors.lastname: Matsuda
keywords: carbon nanotube; exciton; localized; nonlinear; photoluminescence; trapped