Pure optical dephasing dynamics in semiconducting single-walled carbon nanotubes

Matthew W. Graham, Ying Zhong Ma, Alexander A. Green, Mark C Hersam, Graham R. Fleming

Research output: Contribution to journalArticle

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Abstract

We report a detailed study of ultrafast exciton dephasing processes in semiconducting single-walled carbon nanotubes employing a sample highly enriched in a single tube species, the (6,5) tube. Systematic measurements of femtosecond pump-probe, two-pulse photon echo, and three-pulse photon echo peak shift over a broad range of excitation intensities and lattice temperature (from 4.4 to 292 K) enable us to quantify the timescales of pure optical dephasing (T 2*), along with exciton-exciton and exciton-phonon scattering, environmental effects as well as spectral diffusion. While the exciton dephasing time (T 2) increases from 205 fs at room temperature to 320 fs at 70 K, we found that further decrease of the lattice temperature leads to a shortening of the T 2 times. This complex temperature dependence was found to arise from an enhanced relaxation of exciton population at lattice temperatures below 80 K. By quantitatively accounting the contribution from the population relaxation, the corresponding pure optical dephasing times increase monotonically from 225 fs at room temperature to 508 fs at 4.4 K. We further found that below 180 K, the pure dephasing rate (1/T 2*) scales linearly with temperature with a slope of 6.7 0.6 eV/K, which suggests dephasing arising from one-phonon scattering (i.e., acoustic phonons). In view of the large dynamic disorder of the surrounding environment, the origin of the long room temperature pure dephasing time is proposed to result from reduced strength of exciton-phonon coupling by motional narrowing over nuclear fluctuations. This consideration further suggests the occurrence of remarkable initial exciton delocalization and makes nanotubes ideal to study many-body effects in spatially confined systems.

Original languageEnglish
Article number034504
JournalJournal of Chemical Physics
Volume134
Issue number3
DOIs
Publication statusPublished - Jan 21 2011

Fingerprint

Carbon Nanotubes
Single-walled carbon nanotubes (SWCN)
Phonons
carbon nanotubes
excitons
Temperature
Phonon scattering
Photons
echoes
room temperature
tubes
Nanotubes
acoustic scattering
temperature
LDS 751
photons
pulses
Population
Environmental impact
nanotubes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry
  • Medicine(all)

Cite this

Pure optical dephasing dynamics in semiconducting single-walled carbon nanotubes. / Graham, Matthew W.; Ma, Ying Zhong; Green, Alexander A.; Hersam, Mark C; Fleming, Graham R.

In: Journal of Chemical Physics, Vol. 134, No. 3, 034504, 21.01.2011.

Research output: Contribution to journalArticle

Graham, Matthew W. ; Ma, Ying Zhong ; Green, Alexander A. ; Hersam, Mark C ; Fleming, Graham R. / Pure optical dephasing dynamics in semiconducting single-walled carbon nanotubes. In: Journal of Chemical Physics. 2011 ; Vol. 134, No. 3.
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