Ultrafast Mid-Infrared Intra-Excitonic Response of Individualized Single-Walled Carbon Nanotubes

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The quasi-1D confinement and reduced screening of photoexcited charges in single-walled carbon nanotubes (SWNTs) entails strongly-enhanced Coulomb interactions and exciton binding energies. Such amplified electron-hole (e-h) correlations have important implications for both fundamental physics and optoelectronic applications of nanotubes. The availability of"individualized" SWNT ensembles with bright and structured luminescence has rendered specific tube chiralities experimentally accessible. In these samples, evidence for excitonic behavior was found in absorption-luminescence maps, two-photon excited luminescence, or ultrafast carrier dynamics. Here, we report ultrafast mid-infrared (mid-IR) studies of individualized SWNTs, evidencing strong photoinduced absorption around 200 meV in semiconducting tubes of (6,5) and (7,5) chiralities. ... continued below

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Wang, Jigang; Graham, Matt W.; Ma, Yingzhong; Fleming, Graham R. & Kaindl, Robert A. June 29, 2009.

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The quasi-1D confinement and reduced screening of photoexcited charges in single-walled carbon nanotubes (SWNTs) entails strongly-enhanced Coulomb interactions and exciton binding energies. Such amplified electron-hole (e-h) correlations have important implications for both fundamental physics and optoelectronic applications of nanotubes. The availability of"individualized" SWNT ensembles with bright and structured luminescence has rendered specific tube chiralities experimentally accessible. In these samples, evidence for excitonic behavior was found in absorption-luminescence maps, two-photon excited luminescence, or ultrafast carrier dynamics. Here, we report ultrafast mid-infrared (mid-IR) studies of individualized SWNTs, evidencing strong photoinduced absorption around 200 meV in semiconducting tubes of (6,5) and (7,5) chiralities. This manifests the observation of quasi-1D intra-excitonic transitions between different relative-momentum states, in agreement with the binding energy and calculated oscillator strength. Our measurements further reveal a saturation of the photoinduced absorption with increasing phase-space filling of the correlated e-h pairs. The transient mid-IR response represents a new tool, unhindered by restrictions of momentum or interband dipole moment, to investigate the density and dynamics of SWNT excitons.

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  • Journal Name: Nature Physics

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  • Report No.: LBNL-2135E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 1001073
  • Archival Resource Key: ark:/67531/metadc837463

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  • June 29, 2009

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  • May 19, 2016, 3:16 p.m.

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  • June 15, 2016, 9:54 p.m.

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Wang, Jigang; Graham, Matt W.; Ma, Yingzhong; Fleming, Graham R. & Kaindl, Robert A. Ultrafast Mid-Infrared Intra-Excitonic Response of Individualized Single-Walled Carbon Nanotubes, article, June 29, 2009; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc837463/: accessed September 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.