title: Strong Acoustic Phonon Localization in Copolymer-Wrapped Carbon Nanotubes.
abstract: Understanding and controlling exciton-phonon interactions in carbon nanotubes has important implications for producing efficient nanophotonic devices. Here we show that laser vaporization-grown carbon nanotubes display ultranarrow luminescence line widths (120 μeV) and well-resolved acoustic phonon sidebands at low temperatures when dispersed with a polyfluorene copolymer. Remarkably, we do not observe a correlation of the zero-phonon line width with (13)C atomic concentration, as would be expected for pure dephasing of excitons with acoustic phonons. We demonstrate that the ultranarrow and phonon sideband-resolved emission spectra can be fully described by a model assuming extrinsic acoustic phonon localization at the nanoscale, which holds down to 6-fold narrower spectral line width compared to previous work. Interestingly, both exciton and acoustic phonon wave functions are strongly spatially localized within 5 nm, possibly mediated by the copolymer backbone, opening future opportunities to engineer dephasing and optical bandwidth for applications in quantum photonics and cavity optomechanics.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Sarpkaya
authors.forename: Ehsaneh D
authors.initials: ED
authors.lastname: Ahmadi
authors.forename: Gabriella D
authors.initials: GD
authors.lastname: Shepard
authors.affiliation: ‡National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Mistry
authors.affiliation: ‡National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Blackburn
authors.forename: Stefan
authors.initials: S
authors.lastname: Strauf
keywords: acoustic phonon localization; carbon nanotubes; dephasing; excitons; isotope effects