Jan Smotlacha

Analogies in electronic properties of graphene wormhole and perturbed nanocylinder

AbstractnThe electronic properties of the wormhole and the perturbed nanocylinder wereninvestigated using two different methods: the continuum gauge field-theory model thatndeals with the continuum approximation of the surface and the Haydock recursion methodnthat transforms the surface into a simplier structure and deals with the nearest-neighborninteractions. Furthermore, the changes of the electronic properties were investigated fornthe case of enclosing the appropriate structure, and possible substitutes for the enclosernwere derived. Finally, the character of the electron flux through the perturbed wormholenwas predicted from the model based on the multiwalled nanotubes. The effect of then“graphene blackhole” is introduced.n

Electronic structure of disclinated graphene in a uniform magnetic field

The electronic structure in the vicinity of the 1-heptagonal and 1-pentagonal defects in the carbon graphene plane is investigated for the case of hyperboloidal geometry. Using a continuum gauge field-theory model, the local density of states around the Fermi energy is calculated for both cases. In this model, the disclination is represented by a SO(2) gauge vortex and the corresponding metrics follows from the elasticity properties of the graphene membrane. To enhance the interval of energies, a self-consistent perturbation scheme is used. The Landau states are investigated and compared with the predicted values. A discussion on the influence of the Zeeman effect is included.

Spin-orbit interaction in the graphitic nanocone

The Hamiltonian for nanocones with curvature-induced spin-orbit coupling have been derived. The effect of curvature-induced spin-orbit coupling on the electronic properties of graphitic nanocones is considered. Energy spectra for different numbers of the pentagonal defects in the tip of the nanocones are calculated. It was shown that the spin-orbit interaction considerably affects the local density of states of the graphitic nanocone. This influence depends on the number of defects present at the tip of the nanocone. This property could be applied in atomic force microscopy for the construction of the probing tip.

Electronic states of zigzag graphene nanoribbons with edges reconstructed with topological defects

The energy spectrum and electronic density of states (DOS) of zigzag graphene nanoribbons with edges reconstructed with topological defects are investigated within the tight-binding method. In case of the Stone–Wales zz(57) edge the low-energy spectrum is markedly changed in comparison to the pristine zz edge. We found that the electronic DOS at the Fermi level is different from zero at any width of graphene nanoribbons. In contrast, for ribbons with heptagons only at one side and pentagons at another one the energy gap at the Fermi level is open and the DOS is equal to zero. The reason is the influence of uncompensated topological charges on the localized edge states, which are topological in nature. This behavior is similar to that found for the structured external electric potentials along the edges.

Calculation of the electronic structure near the tip of a graphitic nanocone

Abstract In earlier works, the electronic structure of the graphitic nanocone for the long distance from the tip was investigated. Here, we investigate the behaviour of the given nanostructure near the tip where in our approach hybridizations of π orbitals need to be included. In this case, the curvature dependence of π orbital energy has to be included in the model. For this purpose, we use an approximation valid for small values of the corresponding parameters. We consider different numbers of the pentagonal defects in the tip. This localization of the electrons on the nanocone tip could be used as a real application in the electron microscopes.

Electronic structure of disordered graphene with Greenʼs function approach

Abstract The Green functions play a big role in the calculation of the local density of states of the carbon nanostructures. We investigate their nature for the variously oriented and disclinated graphene-like surface. Next, we investigate the case of a small perturbation generated by two heptagonal defects and from the character of the local density of states in the border sites of these defects we derive their minimal and maximal distances on the perturbed cylindrical surface. For this purpose, we transform the given surface into a chain using the Haydock recursion method. We will suppose only the nearest-neighbor interactions between the atom orbitals, in other words, the calculations suppose the short-range potential.

Electronic properties of phosphorene and graphene nanoribbons with edge vacancies in magnetic field

Abstract The graphene and phosphorene nanostructures have a big potential application in a large area of todays research in physics. However, their methods of synthesis still dont allow the production of perfect materials with an intact molecular structure. In this paper, the occurrence of atomic vacancies was considered in the edge structure of the zigzag phosphorene and graphene nanoribbons. For different concentrations of these edge vacancies, their influence on the metallic properties was investigated. The calculations were performed for different sizes of the unit cell. Furthermore, for a smaller size, the influence of a uniform magnetic field was added.

Boundary conditions and Green function approach of the spin-orbit interaction in the graphitic nanocone

The boundary effects affecting the Hamiltonian for the nanocone with curvatureinduced spin orbit coupling were considered and the corresponding electronic structure was calculated. These boundary effects include the spin orbit coupling, the electron mass acquisition and the Coulomb interaction. Different numbers of the pentagonal defects in the tip were considered. The Green function approach into the second order was used for getting more precise results in the case of the spin orbit coupling.

Phosphorene and Graphene Nanoribbons with Vacancies in Magnetic Field

The electronic spectra of the nanostructured materials show an interesting behaviour under the influence of the uniform magnetic field: the dependence of the energy levels on the magnetic field shows a fractal structure. This feature follows from the procedure of the calculation in which the matrix form of the Schrödinger equation is replaced by a system of the Harper equations, where the exponentials with the magnetic factors are supplied to all of the terms. We show the electronic spectra for the case of the narrow phosphorene and graphene zigzag nanoribbons with atomic vacancies and for the nanoribbons equipped with the so-called Stone-Wales defects.

Electronic Properties of Carbon Nanostructures

The carbon nanostructures are perspective materials for the future applications. This has two reasons: first, the hexagonal atomic structure which enables a high molecular variability by placing different kinds of the defects and second, good electronic properties which can be modified for the purpose of the concrete applications with the help of the defects and of the chemical ingredients. A lot of kinds of the nanostructures was investigated. Here, the properties of less common forms will be examined - the graphitic nanocone and graphitic wormhole.