Dispersion in Single-Wall Carbon Nanotube Film: An Application of Bogoliubov–Valatin Transformation for Hamiltonian Diagonalization (original) (raw)

Collective Excitations and Optical Response of Ultrathin Carbon-Nanotube Films

Physical Review Applied

We present a theoretical study of the collective quasiparticle excitations responsible for the electromagnetic response of ultrathin plane-parallel homogeneous periodic single-wall carbon-nanotube arrays and weakly inhomogeneous single-wall carbon-nanotube films. We show that in addition to varying film composition, the collective response can be controlled by varying the film thickness. For single-type nanotube arrays, the real part of the dielectric response shows a broad negative refraction band near a quantum interband transition of the constituent nanotube, whereby the system behaves as a hyperbolic metamaterial at higher frequencies than those classical plasma oscillations have to offer. By decreasing nanotube diameters it is possible to push this negative refraction into the visible region, and using weakly inhomogeneous multitype nanotube films broadens its bandwidth.

Electronic band dispersion of vertically aligned multiwall-carbon nanotubes

Chemical Physics Letters, 2001

We have investigated electronic band structure of the vertically aligned multiwall-carbon nanotubes using angle resolved ultraviolet photoemission spectroscopy and density functional calculations. There exists the finite density of states at the Fermi level, the large 1D subband dispersion, highly degenerate states, and a small momentum periodicity (with a lattice constant of 6.3 Å) in the band dispersion. This strongly suggest that the observed nanotubes are mostly metallic with a chirality of (4k,k), where k is an integer, as predicted from the density functional calculations, although the chirality of the multiwalled nanotubes are likely to be mixed.

Band-gap modulations of double-walled carbon nanotubes under an axial magnetic field

Carbon, 2007

We address here a theoretical study of electronic and transport properties of commensurate double-wall carbon nanotubes (DWCNTs). A single band tight binding hamiltonian is considered and the magnetic field is theoretically described by the Peierls approximation. Weak intershell interactions between a set of neighboring atoms on the walls of the inner and outer tubes are considered. Taking advantage of the real space description, arbitrary configurations of the relative position of the two tubes are taken into account. We study the possibility of Aharonov-Bohm effects in DWCNTs when a magnetic field is applied along the axial direction. The field intensity is found to be more effective than the relative interatomic positions in providing conductance gap modulations.

Electronic structure and dielectric behavior of finite-length single-walled carbon nanotubes

4th IEEE Conference on Nanotechnology, 2004.

The electronic structure and dielectric screening of finite-length armchair carbon nanotubes are studied within a tight-binding model, which well captures the oscillation pattern of the band gap as the tube length increases. We find that: (1) the parallel screening constant || grows almost linearly with the length and shows little dependence on the band gap; (2) the perpendicular screening is strongly related to the band gap and ⊥ converges to its bulk value when the length exceeds tens of radius. Our method is employed to study the depolarization effect of a short (6,6) nanotube in a wet environment, when water is inside the tube. This situation is of interest for biomimetic uses of carbon nanotubes.

Fem Modeling of Periodic Arrays of Multiwalled Carbon Nanotubes

Progress In Electromagnetics Research M, 2012

Multiwalled carbon nanotubes display dielectric properties similar to those of graphite, which can be calculated using the well known Drude-Lorentz model. However, most computational softwares lack the capacity to directly incorporate this model into the simulations. We present the finite element modeling of optical propagation through periodic arrays of multiwalled carbon nanotubes. The dielectric function of nanotubes was incorporated into the model by using polynomial curve fitting technique. The computational analysis revealed interesting metamaterial filtering effects displayed by the highly dense square lattice arrays of carbon nanotubes, having lattice constants of the order few hundred nanometers. The curve fitting results for the dielectric function can also be used for simulating other interesting optical applications based on nanotube arrays.

Superlattice properties of carbon nanotubes in a transverse electric field

Physical Review B, 2005

Electron motion in a (n, 1) carbon nanotube is shown to correspond to a de Broglie wave propagating along a helical line on the nanotube wall. This helical motion leads to periodicity of the electron potential energy in the presence of an electric field normal to the nanotube axis. The period of this potential is proportional to the nanotube radius and is greater than the interatomic distance in the nanotube. As a result, the behavior of an electron in a (n, 1) nanotube subject to a transverse electric field is similar to that in a semiconductor superlattice. In particular, Bragg scattering of electrons from the long-range periodic potential results in the opening of gaps in the energy spectrum of the nanotube. Modification of the bandstructure is shown to be significant for experimentally attainable electric fields, which raises the possibility of applying this effect to novel nanoelectronic devices.

Substrate-induced array of quantum dots in a single-walled carbon nanotube

Nature Nanotechnology, 2009

Single-walled carbon nanotubes are model one-dimensional structures 1-6 . They can also be made into zero-dimensional structures; quantum wells can be created in nanotubes by inserting metallofullerenes 7 , by mechanical cutting 8-10 or by the application of mechanical strain 11 . Here, we report that quantum dot arrays can be produced inside nanotubes simply by causing a misalignment between the nanotube and the k100l direction of a supporting silver substrate. This method does not require chemical or physical treatment of either the substrate or the nanotube. A short quantum dot confinement length of 6 nm results in large energy splittings.

Effects of Finite Length on the Electronic Structure of Carbon Nanotubes

The Journal of Physical Chemistry B, 1999

The electronic structure of finite-length armchair carbon nanotubes has been studied using several ab-initio and semi-empirical quantum computational techniques. The additional confinement of the electrons along the tube axis leads to the opening of a band-gap in short armchair tubes. The value of the band-gap decreases with increasing tube length, however, the decrease is not monotonic but shows a well defined oscillation in short tubes. This oscillation can be explained in terms of periodic changes in the bonding characteristics of the HOMO and LUMO orbitals of the tubes. Finite size graphene sheets are also found to have a finite band-gap, but no clear oscillation is observed. As the length of the tube increases the density of states (DOS) spectrum evolves from that characteristic of a zero-dimensional (0-D) system to that characteristic of a delocalized one-dimensional (1-D)

Geometric boundary effects on the electronic properties of finite carbon nanotubes

Journal of Physics and Chemistry of Solids, 1998

Quantum finite-size effects in carbon nanotubes are studied as a function of tube length L and of the type of end structure used to terminate the tube. The "end" structures considered are: tori, open tubes terminated with H atoms, and various caps formed from hemispherical pieces of fullerenes. With different geometric boundaries there arise distinct asymptotic band-gap behaviors as a function of L: damped oscillations decaying as l/L, monotonic l/L decay, exponentially decaying, and constant. These asymptotic scaling behaviors are categorized and explained in terms of general characteristics of the frontier orbitals. Implications for nanoscale devices are briefly discussed. 8 1997 Elsevier Science Ltd. All rights reserved.