Charge impurity as a localization center for singlet excitons in single-wall nanotubes

Tayo, Benjamin O.; Rotkin, Slava V.

doi:10.1103/physrevb.86.125431

Cited by 21 publications

(23 citation statements)

References 59 publications

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“…2), we reject the hypothesis of defect-localized excitonic states 12 . However, both theoretical 21 and experimental 22 studies have shown that excitons may localize due to the impact of ions adsorbed on the surface of SWNTs, even without covalent bonds. Thus, one should ascribe the X energy level either to the hole-polaron-dressed exciton or to the excitons localized on the sites of physically adsorbed H + ions.…”

Section: Resultsmentioning

confidence: 99%

“…A theoretical investigation by Tayo at al. indicated that charged particles, physisorbed on the surface of SWNTs, might play the role of localization centres for excitons 21 . It was also found experimentally in electrochemically doped nanotubes that both excitons and trions are spatially confined because of adsorbed ions, even without chemical bonding with the nanotube wall 22 .…”

Section: Introductionmentioning

confidence: 99%

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Many-particle excitations in non-covalently doped single-walled carbon nanotubes

Eremin

Obraztsov

Velikanov

et al. 2019

Sci Rep

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Doping of single-walled carbon nanotubes leads to the formation of new energy levels which are able to participate in optical processes. Here, we investigate (6,5)-single walled carbon nanotubes doped in a solution of hydrochloric acid using optical absorption, photoluminescence, and pump-probe transient absorption techniques. We find that, beyond a certain level of doping, the optical spectra of such nanotubes exhibit the spectral features related to two doping-induced levels, which we assign to a localized exciton and a trion T, appearing in addition to an ordinary exciton . We evaluate the formation and relaxation kinetics of respective states and demonstrate that the kinetics difference between E1 and X energy levels perfectly matches the kinetics of the state T. This original finding evidences the formation of trions through nonradiative relaxation via the level, rather than via a direct optical excitation from the ground energy state of nanotubes.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Many-particle excitations in non-covalently doped single-walled carbon nanotubes

Eremin

Obraztsov

Velikanov

et al. 2019

Sci Rep

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“…5(b)) 15 . Qualitatively, the wave-functions of the excitons belonging to different subbands differ only by the extension of the bound relative motion along the tube axis and by a subbanddependent circumferential phase (related to the pseudo angular momentum) 41 . However, the matrix element of the Coulomb interaction is insensitive to the phase factors (the angular momentum is conserved separately for each exciton in either intraband and crossed scatterings since in both cases pictured in Fig.…”

Section: B Broadeningmentioning

confidence: 99%

Intraband and intersubband many-body effects in the nonlinear optical response of single-wall carbon nanotubes

Langlois¹,

Parret²,

Chassagneux³

et al. 2015

Phys. Rev. B

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We report on the nonlinear optical response of a mono-chiral sample of (6,5) single-wall carbon nanotubes by means of broad-band two-color pump-probe spectroscopy with selective excitation of the S11 excitons. By using a moment analysis of the transient spectra, we show that all the nonlinear features can be accurately accounted for by elementary deformations of the linear absorption spectrum. The photo-generation of S11 excitons induces a broadening and a blue shift of both the S11 and S22 excitonic transitions. In contrast, only the S11 transition shows a reduction of oscillator strength, ruling out population up-conversion. These nonlinear signatures result from many-body effects, including phase-space filling, wave-function renormalization and exciton collisions. This framework is sufficient to interpret the magnitude of the observed nonlinearities and stress the importance of intersubband exciton interactions. Remarkably, we show that these intersubband interactions have the same magnitude as the intraband ones and bring the major contribution to the photo-bleaching of the S22 excitonic transition upon S11 excitation through energy shift and broadening.

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“…The finite temperature DOS per electron of the infinite periodic (p) system ρ p (E) is given by: 45,46 …”

Section: Resultsmentioning

confidence: 99%

Band gap engineering in finite elongated graphene nanoribbon heterojunctions: Tight-binding model

Tayo

2015

AIP Advances

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A simple model based on the divide and conquer rule and tight-binding (TB) approximation is employed for studying the role of finite size effect on the electronic properties of elongated graphene nanoribbon (GNR) heterojunctions. In our model, the GNR heterojunction is divided into three parts: a left (L) part, middle (M) part, and right (R) part. The left part is a GNR of width WL, the middle part is a GNR of width WM , and the right part is a GNR of width WR. We assume that the left and right parts of the GNR heterojunction interact with the middle part only. Under this approximation, the Hamiltonian of the system can be expressed as a block tridiagonal matrix. The matrix elements of the tridiagonal matrix are computed using real space nearest neighbor orthogonal TB approximation. The electronic structure of the GNR heterojunction is analyzed by computing the density of states. We demonstrate that for heterojunctions for which WL = WR, the band gap of the system can be tuned continuously by varying the length of the middle part, thus providing a new approach to band gap engineering in GNRs. Our TB results were compared with calculations employing divide and conquer rule in combination with density functional theory (DFT) and were found to agree nicely. I. INTRODUCTIONGraphene is a two-dimensional (2D) allotrope of carbon with excellent electronic and mechanical properties, making it suitable for multiple applications in nanoscale electronics and nanophotonics. 1,2 A major deficiency in graphene's properties is the absence of a band gap rendering it impossible for use in switching circuits. 3 Several approaches have been used to induce a band gap in graphene such as electrically gated bilayer graphene, 4-6 substrate induced band gap, 7,8 or isoelectronic codoping with boron and nitrogen. 9 Recently, it has become possible to engineer the band gap of graphene by etching or patterning along a given direction to produce ultra narrow quasi one-dimensional (1D) nano sheets referred to as graphene nanoribbons (GNRs) [10][11][12] with remarkable properties such as width-dependent tunable band gaps, exciton-dominated optical spectra, and room temperature ballistic transport. [13][14][15] As quasi 1D materials, GNRs are extremely sensitive to their surrounding conditions, which provides a route for manipulating their electronic properties. Additionally, other factors such as finite size effect, 16,17 edge effect, 18-23 and the presence of strain 24-27 could be used to effectively tune the electronic properties GNRs.

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Charge impurity as a localization center for singlet excitons in single-wall nanotubes

Cited by 21 publications

References 59 publications

Many-particle excitations in non-covalently doped single-walled carbon nanotubes

Many-particle excitations in non-covalently doped single-walled carbon nanotubes

Intraband and intersubband many-body effects in the nonlinear optical response of single-wall carbon nanotubes

Band gap engineering in finite elongated graphene nanoribbon heterojunctions: Tight-binding model

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