共查询到20条相似文献,搜索用时 15 毫秒
1.
Afshin Moradi 《Applied Physics A: Materials Science & Processing》2013,113(1):97-100
The properties of surface plasmon–polariton modes in metallic two-walled carbon nanotubes are studied, taking into account the retardation effects. The dispersion relation of surface waves is obtained, by solving Maxwell and hydrodynamic equations with appropriate boundary conditions. Numerical results show that the difference between plasmon and plasmon–polariton modes is strongly dependent on the inner-outer radii of the system but only in the long-wavelength cases. 相似文献
2.
Afshin Moradi 《中国物理 B》2013,(6):352-355
The scattering of electromagnetic wave by an array of parallel metallic single-walled carbon nanotubes is investigated based on the boundary-value method. Electronic excitations over each nanotube surface are modeled as an infinitesimally thin cylindrical layer of the free-electron gas. The scattering cross section of both transverse magnetic (TM) and transverse electric (TE) uniform plane waves by the system at normal incidences is obtained. 相似文献
3.
The absorption cross section of highly luminescent individual single-walled carbon nanotubes is determined using time-resolved and cw luminescence spectroscopy. A mean value of approximately 1 x 10(-17) cm2 per carbon atom is obtained for (6,5) tubes excited at their second optical transition, and corroborated by single tube photothermal absorption measurements. Biexponential luminescence decays are systematically observed, with short and long lifetimes around 45 and 250 ps. This behavior is attributed to the band edge exciton fine structure with a dark level lying a few meV below a bright one. 相似文献
4.
Souza Filho AG Kobayashi N Jiang J Grüneis A Saito R Cronin SB Mendes Filho J Samsonidze GG Dresselhaus G Dresselhaus MS 《Physical review letters》2005,95(21):217403
In this Letter, we report the effects of strain on the electronic properties of single-wall carbon nanotubes. When we normalize the electronic transition energies to the corresponding values obtained for unstrained tubes, we obtain that, regardless of the tube diameter, all the data collapse onto universal curves following an n - m = constant family pattern. In the case of metallic tubes, quantum interference effects on the Raman cross section are predicted for strained tubes when the energies of the lower and the upper components have nearly the same values. Experimental evidence for the strain-induced Raman cross section changes is observed in single nanotube spectroscopy. 相似文献
5.
Direct measurement of the polarized optical absorption cross section of single-wall carbon nanotubes
We determine optical absorption cross sections of single-wall carbon nanotubes for visible light copolarized and cross polarized with respect to the nanotube axis. The need for perfectly aligned ensembles in absorbance measurements is eliminated by using Raman scattering to measure the nematic order parameter in magnetically aligned nanotube suspensions. The absorbance data allow the first quantitative, spectral comparisons with theories of local field depolarization, and provide benchmark spectra for simple, rapid, and quantitative measurements of alignment within nanotube dispersions. 相似文献
6.
We present first-principles calculations of quantum transport which show that the resistance of metallic carbon nanotubes can be changed dramatically with homogeneous transverse electric fields if the nanotubes have impurities or defects. The change of the resistance is predicted to range over more than 2 orders of magnitude with experimentally attainable electric fields. This novel property has its origin that backscattering of conduction electrons by impurities or defects in the nanotubes is strongly dependent on the strength and/or direction of the applied electric fields. We expect this property to open a path to new device applications of metallic carbon nanotubes. 相似文献
7.
Guinea F 《Physical review letters》2005,94(11):116804
The nonhomogeneity of the charge distribution in a carbon nanotube leads to the formation of an excitonic resonance, in a way similar to the one observed in x-ray absorption in metals. As a result, a positive anomaly at low bias appears in the tunneling density of states. This effect depends on the screening of the electron-electron interactions by metallic gates, and it modifies the coupling of the nanotube to normal and superconducting electrodes. 相似文献
8.
《Journal of Physics and Chemistry of Solids》2002,63(6-8):1281-1284
NMR relaxation rate, T1−1, of the metallic carbon nanotube is discussed based on Tomonaga–Luttinger-liquid theory. It is found that the Coulomb interaction leads to increase of (T1T)−1 by a power law with decreasing temperature, T. The dependence on temperature of (T1T)−1 in the multi-wall nanotube (MWNT) is shown to be strongly suppressed by existence of the metallic shells in the MWNTs. 相似文献
9.
The problem of dynamics of propagation of extremely short optical pulses (light bullets) with a Bessel cross section in inhomogeneous medium of carbon nanotubes has been considered. It is numerically shown that the optical pulse propagation is stable and steady. 相似文献
10.
We have calculated the differential conductance of metallic carbon nanotubes by the scatter matrix methon.It is found that the differential conductance of metallic nanotube-based devices oscillates as a function of the bias voltage between the two leads and the gate voltage.Oscillation period T is directly proportional to the reciprocal of nanotube length.In addition,we found that electronic transport properties are sensitive to variation of the length of the nanotube. 相似文献
11.
Using the -band tight-binding (TB) model and the quantum box boundary
condition, we have discussed how both of the applied strain and
finite-length affect the energy bands of metallic carbon nanotubes (CNTs).
It is found that, for finite-length CNTs, energy gap for the armchair tube
under uniaxial strain and metallic zigzag tube under torsional strain will
oscillate with increasing strain, which do not exist in the case of
infinite-length CNTs, and will be able to be observed by experiments in
future. 相似文献
12.
We present theoretical analysis of plasmon dispersion in single-walled metallic carbon nanotubes (SWCNTs) in the presence of low-frequency electromagnetic radiation, based on classical electrodynamic formulations and linearized hydrodynamic model. We assume that metallic carbon nanotubes (CNTs) are charged due to the field emission, and hence the metallic nanotubes can be regarded as charged dust rods surrounded by degenerate electrons and ions. Calculations are performed for the transverse electric (TE) and transverse magnetic (TM) waves, respectively, by solving the Maxwell and hydrodynamic equations with appropriate boundary conditions. 相似文献
13.
The dc Josephson effect is investigated in a single-walled metallic carbon nanotube connected to two superconducting leads. In particular, by using the Luttinger liquid theory, we analyze the effects of the electron-electron interaction on the supercurrent. We find that in the long junction limit the strong electronic correlations of the nanotube, together with its peculiar band structure, induce oscillations in the critical current as a function of the junction length and/or the nanotube electron filling. These oscillations represent a signature of the Luttinger liquid physics of the nanotube, for they are absent if the interaction is vanishing. We show that this effect can be exploited to reverse the sign of the supercurrent, realizing a tunable π-junction. 相似文献
14.
To accommodate extra electrons or holes injected into a single-wall carbon nanotube, carbon-carbon bonds adjust their lengths. Resulting changes in carbon-nanotube length as a function of charge injection provide the basis for electromechanical actuators. We show that a key mechanism at low injection levels, modulation of electron kinetic energy, provides nanotube deformations that are both anisotropic and strongly dependent on nanotube structure. Nanotubes can exhibit both expansion and contraction, as well as nonmonotonic size changes. The magnitude of the actuation response of semiconducting carbon nanotubes may be substantially larger than that of graphite. 相似文献
15.
Wang F Cho DJ Kessler B Deslippe J Schuck PJ Louie SG Zettl A Heinz TF Shen YR 《Physical review letters》2007,99(22):227401
Excitons are generally believed not to exist in metals because of strong screening by free carriers. Here we demonstrate that excitonic states can in fact be produced in metallic systems of a one-dimensional character. Using metallic single-walled carbon nanotubes as a model system, we show both experimentally and theoretically that electron-hole pairs form tightly bound excitons. The exciton binding energy of 50 meV, deduced from optical absorption spectra of individual metallic nanotubes, significantly exceeds that of excitons in most bulk semiconductors and agrees well with ab initio theoretical predictions. 相似文献
16.
Farhat H Berciaud S Kalbac M Saito R Heinz TF Dresselhaus MS Kong J 《Physical review letters》2011,107(15):157401
We present experimental measurements of the electronic contribution to the Raman spectra of individual metallic single-walled carbon nanotubes (MSWNTs). Photoexcited carriers are inelastically scattered by a continuum of low-energy electron-hole pairs created across the graphenelike linear electronic subbands of the MSWNTs. The optical resonances in MSWNTs give rise to well-defined electronic Raman peaks. This resonant electronic Raman scattering is a unique feature of the electronic structure of these one-dimensional quasimetals. 相似文献
17.
P. Partovi-Azar A. Namiranian 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(1):89-95
Nonlinear quantum conductance in finite metallic single-wall carbon nanotubes due to presence of a single defect has been
studied theoretically using π-orbital tight-binding model. The correction to the conductance induced by defects is sensitively
dependent on wavefunction amplitudes of contributing electronic states. It has been shown that by calculating this correction
to the first order, we can delineate the position of carbon atoms on tubular surface. It can also be used to specify the SWCNT
at hand and its level spacing. 相似文献
18.
We show that the local temperature dependence of thermalized electron and phonon populations along metallic carbon nanotubes is the main reason behind the nonlinear transport characteristics in the high bias regime. Our model is based on the solution of the Boltzmann transport equation considering both optical and zone boundary phonon emission as well as absorption by charge carriers. It also assumes a local temperature along the nanotube, determined self-consistently with the heat transport equation. By using realistic transport parameters, our results not only reproduce experimental data for electronic transport but also provide a coherent interpretation of thermal breakdown under electric stress. In particular, electron and phonon thermalization prohibits ballistic transport in short nanotubes. 相似文献
19.
F. Buonocore 《哲学杂志》2013,93(7):1097-1105
In this paper we investigate nitrogen- and boron-doped zigzag and armchair single-wall carbon nanotubes (SWNTs) with theoretical models based on the density functional theory. We take into account nitrogen and boron doping for two isomers in which substitutive atoms are on opposite sides of the tube, but only in one isomer the impurity sites are symmetrical with respect to the diameter. The band structures show a strong hybridization with impurity orbitals that change the original band structure. Although the two isomers of armchair SWNT exhibit the same formation energy, their band structures are different. Indeed asymmetrical isomers are gapless and exhibit a crossing of valence and conduction bands at k?=?π/c, leading to metallic SWNTs. Band structures of symmetrical isomers, on the other hand, exhibit an energy gap of 0.4?eV between completely filled valence and empty conduction bands. We use density of charge in order to understand this difference. In zigzag SWNT an impurity band is introduced in the energy gap and for N doping this band is just partially occupied in such a way that the electronic behaviour is reversed from semiconductor to metallic. Whereas for a given isomer armchair SWNT shows similar behaviours of N- and B-doped structures, B-doped zigzag SWNTs present different band structure and occupation compared to the N-doped case. 相似文献