Chirality dependence of exciton effects in single-wall carbon nanotubes: Tight-binding model

Jiang, Jie; Saito, Riichiro; Samsonidze, Ge. G.; Jório, Ado; Chou, S. G.; Dresselhaus, G.; Dresselhaus, M. S.

doi:10.1103/physrevb.75.035407

Cited by 228 publications

(291 citation statements)

References 49 publications

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“…16 represents the non-negligible but small contribution of residual non-armchair ν = 0 impurities [(10,7) and (11,8)] and a qualitative measure of the larger Raman cross-section such species have as compared to armchair tubes. 104 Another interesting observation to make is that of the larger line width of the G + feature observed for the (7,7) spectrum taken at 500 nm in Fig. 16 than that of the (7,7) sample taken at 502 nm in Fig.…”

Section: G-band Raman Signatures Of Armchair and Non-armchair ν mentioning

confidence: 96%

Fundamental optical processes in armchair carbon nanotubes

Hároz

Duque

et al. 2013

Nanoscale

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Single-wall carbon nanotubes provide ideal model 1-D condensed matter systems in which to address fundamental questions in many-body physics, while, at the same time, they are leading candidates for building blocks in nanoscale optoelectronic circuits. Much attention has been recently paid to their optical properties, arising from 1-D excitons and phonons, which have been revealed via photoluminescence, Raman scattering, and ultrafast optical spectroscopy of semiconducting carbon nanotubes. On the contrary, dynamical properties of metallic nanotubes have been poorly explored, although they are expected to provide a novel setting for the study of electron-hole pairs in the presence of degenerate 1-D electrons. In particular, (n,n)-chirality, or armchair, metallic nanotubes are truly gapless with massless carriers, ideally suited for dynamical studies of Tomonaga-Luttinger liquids. Unfortunately, progress towards such studies has been slowed by the inherent problem of nanotube synthesis whereby both semiconducting and metallic nanotubes are produced. Here, we use post-synthesis separation methods based on density gradient ultracentrifugation and DNAbased ion-exchange chromatography to produce aqueous suspensions strongly enriched in armchair nanotubes. Through resonant Raman spectroscopy of the radial breathing mode phonons, we provide macroscopic and unambiguous evidence that density gradient ultracentrifugation can enrich armchair nanotubes. Furthermore, using conventional, optical absorption spectroscopy in the nearinfrared and visible range, we show that interband absorption in armchair nanotubes is strongly excitonic. Lastly, by examining the G-band mode in Raman spectra, we determine that observation of the broad, lower frequency (G − ) feature is a result of resonance with non-armchair "metallic" nanotubes. These findings regarding the fundamental optical absorption and scattering processes in metallic carbon nanotubes lay the foundation for further spectroscopic studies to probe many-body physical phenomena in one dimension.

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Section: G-band Raman Signatures Of Armchair and Non-armchair ν mentioning

confidence: 96%

Fundamental optical processes in armchair carbon nanotubes

Hároz

Duque

et al. 2013

Nanoscale

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“…To further refine the results, the calculation can be modified to include additional nearest neighbor carbon atoms and overlap integrals, 99 the effects of curvature, 100 and exciton influences (vide infra). 101,102 For example, because tight binding does not account for the curvature of the SWNT, it is only a good approximation for large diameter nanotubes (d t > 1.5 nm)…”

Section: Swnt Electronic Band Structurementioning

confidence: 99%

“…For example, despite predictions that the perpendicular transition will be mostly suppressed, cross-polarized PLE studies for an ensemble of SWNTs indicate that the E 12 energy is close to the E 22 excitation energy, and these transitions can be readily observed. 102,226 Other factors that could account for the observation of fluorescence from misaligned SWNTs include the possibility of imperfect laser polarization or depolarization effects associated with other optics in our setup such as the high NA objective.…”

Section: Correlated Fluorescence and Topographymentioning

confidence: 99%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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Single-walled carbon nanotubes (SWNTs) are cylindrical graphitic molecules that have remained at the forefront of nanomaterials research since 1991, largely due to their exceptional and unusual mechanical, electrical, and optical properties. The motivation for understanding how nanotubes interact with light (i.e., SWNT photophysics) is both fundamental and applied. Individual nanotubes may someday be used as superior near-infrared fluorophores, biological tags and sensors, and components for ultrahigh-speed optical communications systems. Establishing an understanding of basic nanotube photophysics is intrinsically significant and should enable the rapid development of such innovations. Unlike conventional molecules, carbon nanotubes are synthesized as heterogeneous samples, composed of molecules with different diameters, chiralities, and lengths. Because a nanotube can be either metallic or semiconducting depending on its particular molecular structure, SWNT samples are also mixtures of conductors and semiconductors. Early progress in understanding the optical characteristics of SWNTs was limited because nanotubes aggregate when synthesized, causing a mixing of the energy states of different nanotube structures. Recently, significant improvements in sample preparation have made it possible to isolate individual nanotubes, enabling many advances in characterizing their optical properties. In this Account, single-molecule confocal microscopy and spectroscopy were implemented to study the fluorescence from individual nanotubes. Single-molecule measurements naturally circumvent the difficulties associated with SWNT sample inhomogeneities. Intrinsic SWNT photoluminescence has a simple narrow Lorentzian line shape and a polarization dependence, as expected for a one-dimensional system. Although the local environment heavily influences the optical transition wavelength and intensity, single nanotubes are exceptionally photostable. In fact, they have the unique characteristic that their single molecule fluorescence intensity remains constant over time; SWNTs do not “blink” or photobleach under ambient conditions. In addition, transient absorption spectroscopy was used to examine the relaxation dynamics of photoexcited nanotubes and to elucidate the nature of the SWNT excited state. For metallic SWNTs, very fast initial recovery times (300–500 fs) corresponded to excited-state relaxation. For semiconducting SWNTs, an additional slower decay component was observed (50–100 ps) that corresponded to electron–hole recombination. As the excitation intensity was increased, multiple electron–hole pairs were generated in the SWNT; however, these e−h pairs annihilated each other completely in under 3 ps. Studying the dynamics of this annihilation process revealed the lifetimes for one, two, and three e−h pairs, which further confirmed that the photoexcitation of SWNTs produces not free electrons but rather one-dimensional bound electron–hole pairs (i.e., excitons). In summary, nanotube photophysics is a rapidly developing area o...

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“…We have not performed any detailed calculation of the exciton binding energies 41,42 or of the exciton-phonon coupling matrix elements 18,39 . Furthermore, for a complete description of the asymmetry within this model, knowledge of the exciton lifetimes is also necessary.…”

Section: Fifth-order Raman Processesmentioning

confidence: 99%

Asymmetric excitation profiles in the resonance Raman response of armchair carbon nanotubes

et al. 2015

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We performed tunable resonance Raman spectroscopy on samples highly enriched in the (5,5), (6,6), (7,7), and (8,8) armchair structures of metallic single-wall carbon nanotubes. We present Raman excitation profiles (REPs) for both the radial breathing mode and G-band phonons of these species. G-band excitation profiles are shown to resolve the expected incoming and outgoing resonances of the scattering process. Notably, the profiles are highly asymmetric, with the higherenergy outgoing resonance weaker than the incoming resonance. These results are comparable to the asymmetric excitation profiles observed previously in semiconducting nanotubes, introduce a new electronic type, and broaden the structural range over which the asymmetry is found to exist. Modeling of the behavior with a third-order quantum model that accounts for the k -dependence in energies and matrix elements, without including excitonic effects, is found to be insufficient for reproducing the observed asymmetry. We introduce an alternative fifth-order model in which the REP asymmetry arises from quantum interference introduced by phonon-mediated state-mixing between the E M 11 and K-momentum excitons. Such state-mixing effectively introduces a nuclear coordinate dependence in the transition dipole moment and thus may be viewed as a non-Condon effect from a molecular perspective. This result unifies a molecular-like picture of nanotube transitions (introduced by their excitonic nature) with a condensed matter approach for describing their behavior.

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Chirality dependence of exciton effects in single-wall carbon nanotubes: Tight-binding model

Cited by 228 publications

References 49 publications

Fundamental optical processes in armchair carbon nanotubes

Fundamental optical processes in armchair carbon nanotubes

Photophysics of Individual Single-Walled Carbon Nanotubes

Asymmetric excitation profiles in the resonance Raman response of armchair carbon nanotubes

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