Excitons in metallic carbon nanotubes with Aharonov-Bohm flux

Uryu, Seiji; Ando, Tsuneya

doi:10.1103/physrevb.77.205407

Cited by 24 publications

(18 citation statements)

References 62 publications

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“…As a note, the higher-order k ·p formalism has been shown to be equivalent with tightbinding approach with regards to both the curvatureinduced band gap and trigonal-warping effects. [44][45][46] The trigonal-warping effect is most clearly shown in a comparison of the first massive bands (|q| = 1) for armchair and non-armchair species in Fig. 1.…”

Section: Band Structure and Selection Rules For Optical Transitiomentioning

confidence: 99%

“…While excitons are commonly associated with the optical transitions and spectra of semiconductors, recent experiments [54][55][56][57] and theoretical studies 46,[58][59][60][61] have reported the strong influence of excitonic effects in the optical spectra and band structure of metallic SWCNTs. While the optical selection rules governing absorption and resonant Raman processes remain unaffected, 46 the energy positions and line shapes of the major optical features are modified as a result of the formation of excitons. Allowed optical transitions for excitons associated with a particular electronic state still obey the earlier optical selection rules with the additional constraint that only 1 of the 16 possible excitonic states (after taking into account valley and spin degeneracies) is optically active.…”

Section: Excitonic Effectsmentioning

confidence: 99%

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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: Band Structure and Selection Rules For Optical Transitiomentioning

confidence: 99%

Section: Excitonic Effectsmentioning

confidence: 99%

Fundamental optical processes in armchair carbon nanotubes

Hároz

Duque

et al. 2013

Nanoscale

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“…The small binding energy in the static case leads to asymmetric absorption spectra [4,5], as seen in Fig. 2, where the Coulomb coupling (e 2 /κL)(2πγ/L) −1 = 0.16 is used.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…The exciton peak position is determined by the balance of the above two opposite effects so that the screening should be carefully considered, especially when there are mobile carriers. In this study, we clarify the stability of exciton states in the metallic nanotubes under the dynamic screening by comparing the results with those in the previous studies [4,5] based on the static screening.…”

Section: Introductionmentioning

confidence: 85%

“…The excitons in semiconducting carbon nanotubes have large binding energies of the order of hundreds of milielectron volts owing to the Coulomb interaction in one-dimensional systems. Such excitonic peaks are observed in optical spectra even for metallic carbon nanotubes [3][4][5][6], while its exciton binding energies are supposed to be too small to be confirmed due to strong metallic screening.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Dynamic Screening on Excitons in Metallic Carbon Nanotubes

Tomio¹,

Suzuura²

2015

Proceedings of the International Symposium “Nanoscience and Quantum Physics 2012” (nanoPHYS’12)

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Excitonic effects and the absorption spectra of metallic carbon nanotubes are studied in an effectivemass scheme by taking dynamic screening into consideration. The result shows that the dynamic screening makes the excitons in metallic carbon nanotubes more stable than the static screening neglecting the retardation in the screening of Coulomb interaction. The dynamic screening effect appears only in the exciton states and it is hardly seen in continuum states.

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Optoelectronic Properties of Single‐Wall Carbon Nanotubes

et al. 2012

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Single-wall carbon nanotubes (SWCNTs), with their uniquely simple crystal structures and chirality-dependent electronic and vibrational states, provide an ideal laboratory for the exploration of novel 1D physics, as well as quantum engineered architectures for applications in optoelectronics. This article provides an overview of recent progress in optical studies of SWCNTs. In particular, recent progress in post-growth separation methods allows different species of SWCNTs to be sorted out in bulk quantities according to their diameters, chiralities, and electronic types, enabling studies of (n,m)-dependent properties using standard macroscopic characterization measurements. Here, a review is presented of recent optical studies of samples enriched in 'armchair' (n = m) species, which are truly metallic nanotubes but show excitonic interband absorption. Furthermore, it is shown that intense ultrashort optical pulses can induce ultrafast bandgap oscillations in SWCNTs, via the generation of coherent phonons, which in turn modulate the transmission of a delayed probe pulse. Combined with pulse-shaping techniques, coherent phonon spectroscopy provides a powerful method for studying exciton-phonon coupling in SWCNTs in a chirality-selective manner. Finally, some of the basic properties of highly aligned SWCNT films are highlighted, which are particularly well-suited for optoelectronic applications including terahertz polarizers with nearly perfect extinction ratios and broadband photodetectors.

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Excitons in metallic carbon nanotubes with Aharonov-Bohm flux

Cited by 24 publications

References 62 publications

Fundamental optical processes in armchair carbon nanotubes

Fundamental optical processes in armchair carbon nanotubes

Effects of Dynamic Screening on Excitons in Metallic Carbon Nanotubes

Optoelectronic Properties of Single‐Wall Carbon Nanotubes

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