In an armchair carbon nanotube pn junction the p- and n- regions are separated by a region of a Mott insulator, which can backscatter electrons only in pairs. We predict a quantum-critical behavior in such a pn junction. Depending on the junction's built-in electric field E, its conductance G scales either to zero or to the ideal value G=4e^2/h as the temperature T is lowered. The two types of the G(T) dependence indicate the existence, at some special value of E, of an intermediate quantum critical point with a finite conductance G<4e^2/h. This makes the pn junction drastically different from a simple barrier in a Luttinger liquid.
We report the one-electron spectrum and eigenstates of infinite achiral and chiral $(2m,m)$ carbon nanotubes found by using the analytic solution to the Schrödinger equation for the tight-binding Hückel-type Hamiltonian. With the help of matching the wave functions on the interfaces between the regions, where electrons have different site energies, we find and compare the transmission coefficients for zigzag, armchair and chiral nanotubes subjected to the action of an applied step-like potential. The correspondence between the nanotube band structure and the energy dependence of the transmissi…
Local Semiconducting Transition in Armchair Carbon Nanotubes: The Effect of Periodic Bi-site Perturbation on Electronic and Transport Properties of Carbon Nanotubes
The changes of dynamical behaviour of a single fullerene molecule inside an armchair carbon nanotube caused by the structural Peierls transition in the nanotube are considered. The structures of the smallest C20 and Fe@C20 fullerenes are computed using the spin-polarized density functional theory. Significant changes of the barriers for motion along the nanotube axis and rotation of these fullerenes inside the (8,8) nanotube are found at the Peierls transition. It is shown that the coefficients of translational and rotational diffusions of these fullerenes inside the nanotube change by several…
Relation between dispersion lines and conductance of telescoped armchair double-wall nanotubes analyzed using perturbation formulas and first-principles calculations
Interlayer Conductance in the Armchair Nanotube -- Zigzag Graphene Ribbon Parallel Contact: Theoretical Proposal of Detection of Wavefunction Growing from the Edge to the Center in the Graphene Ribbon
The intertube conductance $G$ of the parallel side contacted armchair nanotubes is calculated by Landauer's formula as a function of the Fermi level $E$. When the intertube difference in the dope strength is large enough, a resonant peak dominant over the others appears in the $E$-$G$ curve. The overlap length and the interlayer configuration do not influence the resonant energy. The intervalley transmission at the resonant peak works as a reverser and a filter of the valley current.
Properties of bulk and boundaries of materials can, in general, be quite different, both for topological and non-topological reasons. One of the simplest boundary problems to pose is the tight-binding problem of noninteracting electrons on a finite honeycomb lattice. Despite its simplicity, the problem is quite rich and directly related to the physics of graphene. We revisit this long-studied problem and present an analytical derivation of the electron spectrum and wave functions for graphene rectangular derivatives. We provide an exact analytical description of extended and localized states, …
Partially overlapping two parallel armchair nanotubes are investigated theoretically with the $π$ orbital tight bonding model. Considering the interlayer Hamiltonian as perturbation, we obtain approximate analytical formulas of the interlayer transmission rates $T_{σ',σ}$ from channel $σ$ to $σ'$ for all the four combinations $(σ',σ)=(\pm,\pm)$ and $(\pm,\mp)$, where suffixes $+$ and $-$ represent symmetric and anti-symmetric channels, respectively, with respect to the mirror plane of each tube. Landauer's formula conductance is equal to the sum of them in units of $2e^2/h$. According to the p…
Phonon Dispersion in Chiral Single Wall Carbon Nanotubes
从$6\times 6$动力学矩阵出发，计算了手性单壁碳纳米管的声子色散。本文是G. D. Mahan和Gun Sang Jeon在扶手椅和锯齿形纳米管上的工作。[see P. R. B、{ \bf 70}，075405（2004）]。我们采用弹簧-质量模型，并采用\cite{M2}建议的适当声子势。我们可以计算任意手性的单壁碳纳米管在$Γ$点附近的色散。结果与Mahan et. al的扶手椅型和锯齿型单壁碳纳米管的结果。
We numerically investigate the electronic transport properties of graphene nanoribbons and carbon nanotubes with inter-valley coupling, e.g., in \sqrt{3}N \times \sqrt{3}N and 3N \times 3N superlattices. By taking the \sqrt{3} \times \sqrt{3} graphene superlattice as an example, we show that tailoring the bulk graphene superlattice results in rich structural configurations of nanoribbons and nanotubes. After studying the electronic characteristics of the corresponding armchair and zigzag nanoribbon geometries, we find that the linear bands of carbon nanotubes can lead to the Klein tunnelling-l…
We present a novel floating catalyst synthesis route for individual, i.e. non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3-4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up …
We present a symmetry-adapted real-space formulation of Kohn-Sham density functional theory for cylindrical geometries and apply it to the study of large X (X=C, Si, Ge, Sn) nanotubes. Specifically, starting from the Kohn-Sham equations posed on all of space, we reduce the problem to the fundamental domain by incorporating cyclic and periodic symmetries present in the angular and axial directions of the cylinder, respectively. We develop a high-order finite-difference parallel implementation of this formulation, and verify its accuracy against established planewave and real-space codes. Using …
Using large-scale DFT calculations, we have investigated the structural and electronic properties of both armchair and zigzag graphdiyne nanotubes as a function of size. To provide insight in these properties, we present new detailed calculations of the structural relaxation energy, effective electron/hole mass, and size-scaling of the bandgap as a function of size and chirality using accurate screened-exchange DFT calculations. These calculations provide a systematic evaluation of the structural and electronic properties of the largest graphdiyne nanotubes to date - up to 1,296 atoms and 23,3…
We use the robust nearest-neighbour tight-binding approximation to study on the same footing interband dipole transitions in narrow-bandgap carbon nanotubes and graphene nanoribbons. It is demonstrated that curvature effects in metallic single-walled carbon nanotubes and edge effects in gapless graphene nanoribbons not only open up bang gaps, which typically correspond to THz frequencies, but also result in a giant enhancement of the probability of optical transitions across these gaps. Moreover, the matrix element of the velocity operator for these transitions has a universal value (equal to …
A recent claim of superfluid behaviour of parahydrogen adsorbed inside armchair carbon nanotubes [M. Rossi and F. Ancilotto, Phys. Rev. B 94, 100502 (2016)] is disproven by means of first principle computer simulations. Conclusive numerical evidence shows that the low temperature equilibrium thermodynamic phase of parahydrogen adsorbed inside a (10,10) armchair nanotube features a crystalline shell adsorbed on the inner surface of the tube, and a well separated quasi one-dimensional central column showing no evidence of possible fluid or superfluid behaviour. Rather, the system is quasi-crysta…
In this paper we study the effect of absorption peak correlation in finite length carbon nanotubes and graphene nanoribbons. It is shown, in the orthogonal π-orbital tight-binding model with the nearest neighbor approximation, that if the ribbon width is a half of the tube circumference the effect takes place for all achiral ribbons (zigzag, armchair and bearded), and corresponding tubes, starting from lengths of about 30 nm. This correlation should be useful in designing nanoribbon-based optoelectronics devices fully integrated into a single layer of graphene.
We propose an ab-initio combination of the Linear Muffin-Tin Orbital and the Recursion Methods to study the effect of extended Stone-Wales defects in single layer Carbon nanotubes. We have successfully applied this to zigzag and armchair tubes. The methodology involves no intrinsic mean-field like assumptions or external parameter fitting. As defects proliferate, the low density of states near the Fermi levels of the pristine tubes is filled with defect states. The increase of DOS at the Fermi level leads to enhanced conduction, which indicates enhanced metallicity due to SW defects in the nan…
