Coherent Phonon Dynamics in Semiconducting Carbon Nanotubes: A Quantitative Study of Electron-Phonon Coupling

Lüer, Larry; Gadermaier, Christoph; Crochet, Jared; Hertel, Tobias; Brida, Daniele; Lanzani, Guglielmo

doi:10.1103/physrevlett.102.127401

Cited by 92 publications

(105 citation statements)

References 27 publications

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“…These coherent RBM phonons have been studied experimentally by several groups [51][52][53][54][55][56]. In addition to the lower frequency coherent RBM modes, higher frequency q = 0 coherent G mode phonons have also been observed [57,58].…”

Section: Introductionmentioning

confidence: 96%

Theory of coherent phonons in carbon nanotubes and graphene nanoribbons

Sanders

Nugraha

Sato

et al. 2013

J. Phys.: Condens. Matter

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We survey our recent theoretical studies on the generation and detection of coherent radial breathing mode (RBM) phonons in single-walled carbon nanotubes and coherent radial breathing like mode (RBLM) phonons in graphene nanoribbons. We present a microscopic theory for the electronic states, phonon modes, optical matrix elements and electron-phonon interaction matrix elements that allows us to calculate the coherent phonon spectrum. An extended tight-binding (ETB) model has been used for the electronic structure and a valence force field (VFF) model has been used for the phonon modes. The coherent phonon amplitudes satisfy a driven oscillator equation with the driving term depending on the photoexcited carrier density. We discuss the dependence of the coherent phonon spectrum on the nanotube chirality and type, and also on the graphene nanoribbon mod number and class (armchair versus zigzag). We compare these results with a simpler effective mass theory where reasonable agreement with the main features of the coherent phonon spectrum is found. In particular, the effective mass theory helps us to understand the initial phase of the coherent phonon oscillations for a given nanotube chirality and type. We compare these results to two different experiments for nanotubes: (i) micelle suspended tubes and (ii) aligned nanotube films. In the case of graphene nanoribbons, there are no experimental observations to date. We also discuss, based on the evaluation of the electron-phonon interaction matrix elements, the initial phase of the coherent phonon amplitude and its dependence on the chirality and type. Finally, we discuss previously unpublished results for coherent phonon amplitudes in zigzag nanoribbons obtained using an effective mass theory.

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Section: Introductionmentioning

confidence: 96%

Theory of coherent phonons in carbon nanotubes and graphene nanoribbons

Sanders

Nugraha

Sato

et al. 2013

J. Phys.: Condens. Matter

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“…Up to date, there have been only several studies on ultrafast phenomena in CNTs, 10-14 and early time stage dynamics of photoexcitation of electronic system and subsequent phonon excitation and relaxation was not been well explored. Motivated by the observation of the early time stage dynamics of electron-phonon coupling, Lüer et al 15 have recently investigated the electron-phonon coupling by means of coherent phonon spectroscopy with 10 fs time resolution, where they focused their attention to the high-frequency optical modes rather than the RBMs.In this paper, the coherent oscillation of the RBMs in SWNTs has been measured in various pH environments to show that the subpicosecond relaxation dynamics as well as the coherent phonon spectra of the RBM are very sensitive to the change in the electronic structure of SWNT upon the protonation.The samples of SWNTs were produced via the highpressure catalytic CO decomposition process. To disperse SWNTs in aqueous solution, we used sodium dodecyl sulfate ͑SDS͒.…”

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confidence: 99%

“…Up to date, there have been only several studies on ultrafast phenomena in CNTs, [10][11][12][13][14] and early time stage dynamics of photoexcitation of electronic system and subsequent phonon excitation and relaxation was not been well explored. Motivated by the observation of the early time stage dynamics of electron-phonon coupling, Lüer et al 15 have recently investigated the electron-phonon coupling by means of coherent phonon spectroscopy with 10 fs time resolution, where they focused their attention to the high-frequency optical modes rather than the RBMs.…”

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confidence: 99%

Ultrafast vibrational motion of carbon nanotubes in different pH environments

et al. 2009

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We have used a femtosecond pump-probe impulsive Raman technique to explore the ultrafast dynamics of micelle suspended single-walled carbon nanotubes ͑SWNTs͒ in various pH environments. The structures of coherent phonon spectra of the radial breathing modes exhibit significant pH dependence, to which we attribute the effect of the protonation at the surface of SWNTs, resulting in the modification of electronic properties of semiconductor SWNTs. Analysis of the time-domain data using a time-frequency transformation uncovers also a second transient longitudinal breathing mode, which vanishes after 1 ps of the photoexcitation. DOI: 10.1103/PhysRevB.80.245428 PACS number͑s͒: 78.47.JϪ, 78.67.Ch, 63.22.Gh, 63.20.kd Carbon nanotubes ͑CNTs͒ are one of the most intriguing nanomaterials, which are useful for molecular devices, such as a chemical sensor 1 and a nanomachine capable for medical science. 2 One potential way to realize the nanomachine by the use of CNTs, which can work in biological systems, e.g., a drug delivery system, is to use them in solution with proteins. 2 Therefore, CNT devices will be used in various pH environments in biological systems, e.g., the typical pH of human arterial blood is Ϸ7.4 that is weakly alkaline. Since the chemical reactivity of CNTs is dominated by the fundamental physical processes on their surface, investigation of dynamics at surfaces, such as charge transfer, 3 excitonplasmon coupling, 4 and electron-phonon energy transfer, 5 is crucial to prepare suitable environments for CNT devices.Single-walled carbon nanotubes ͑SWNTs͒ possess simplest structure of CNTs and it has metallic or semiconducting conductivity, depending on the arrangement of carbon atoms, referred as roll-up vectors. 6 Recently frequency-domain spectroscopy has revealed the diameter-selective Raman scattering from radial breathing modes ͑RBMs͒ in SWNT,7,8 where the frequency of the RBMs depended on the inverse of the diameter. 3 Moreover, Strano et al. 9 have investigated the change in the Raman spectra of RBM induced by the protonation and showed that the protons change electronic structure of SWNT, i.e., protonation is band-gap selective and consequently the condition of resonant Raman scattering was modified, depending on the pH values. Coherent phonon spectroscopy is another potential method to study phonon dynamics in time-domain. Up to date, there have been only several studies on ultrafast phenomena in CNTs, 10-14 and early time stage dynamics of photoexcitation of electronic system and subsequent phonon excitation and relaxation was not been well explored. Motivated by the observation of the early time stage dynamics of electron-phonon coupling, Lüer et al. 15 have recently investigated the electron-phonon coupling by means of coherent phonon spectroscopy with 10 fs time resolution, where they focused their attention to the high-frequency optical modes rather than the RBMs.In this paper, the coherent oscillation of the RBMs in SWNTs has been measured in various pH environments to show that the subpic...

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“…In most cases, mixture of CNTs with different chiralities and diameters is used for the measurements, making the analysis of the data complicated. Although single chirality samples are recently available [5,6], it is still required to establish a way to distinguish the chirality of CNTs because the purity is at most in the order of 80 % even in the single chirality samples.…”

Section: Introductionmentioning

confidence: 99%

“…The electronic structure of CNTs changes from semiconductors to metals depending on the chirality [1]. The dynamics of carriers and electron-phonon coupling could also show strong dependence on their electronic structures, and thereby various ultrafast measurements have been investigated [2][3][4][5]. In most cases, mixture of CNTs with different chiralities and diameters is used for the measurements, making the analysis of the data complicated.…”

Section: Introductionmentioning

confidence: 99%