Radiation Emission by Electrons Channeling in Bent Silicon Crystals

Results of numerical simulations of electron channeling and emission spectra are reported for straight and uniformly bent silicon crystal. The projectile trajectories are computed using the newly developed module [1] of the MBN Explorer package [2,3]. The electron channeling along Si(110) crystallographic planes is studied for the projectile energy 855 MeV.Comment: 9 pages, 7 figures; submitted to European Physical Journal D. arXiv admin note: text overlap with arXiv:1307.678

Carbon nanotube array as a van der Waals two-dimensional hyperbolic material

We use an ab-initio approach to design and study a novel two-dimensional material - a planar array of carbon nanotubes separated by an optimal distance defined by the van der Waals interaction. We show that the energy spectrum for an array of quasi-metallic nanotubes is described by a strongly anisotropic hyperbolic dispersion and formulate a model low-energy Hamiltonian for its semi-analytical treatment. Periodic-potential-induced lifting of the valley degeneracy for an array of zigzag narrow-gap nanotubes leads to the band gap collapse. In contrast, the band gap is opened in an array of gapless armchair tubes. These unusual spectra, marked by pronounced van Hove singularities in the low-energy density of states, open the opportunity for interesting physical effects and prospective optoelectronic applications

Hybridization-related correction to the jellium model for fullerenes

We introduce a new type of correction for a more accurate description of fullerenes within the spherically symmetric jellium model. This correction represents a pseudopotential which originates from the comparison between an accurate ab initio calculation and the jellium model calculation. It is shown that such a correction to the jellium model allows one to account, at least partly, for the sp2-hybridization of carbon atomic orbitals. Therefore, it may be considered as a more physically meaningful correction as compared with a structureless square-well pseudopotential which has been widely used earlier.Comment: 16 pages, 10 figure

Photoionization of the fullerene ion C60+

Photoionization cross section of the fullerene ion C60+ has been calculated within a single-electron approximation and also by using a consistent many-body theory accounting for many-electron correlations.Comment: 8 pages, 3 figure

Spin transport in an Aharonov-Bohm ring with exchange interaction

We investigate spin-dependent conductance through a quantum Aharonov-Bohm ring containing localized electrons which interact with the propagating flow of electrons via exchange interaction of the ferromagnetic or antiferromagnetic type. We analyze the conductance oscillations as a function of both the chemical potential (particle concentration) and external magnetic field. It is demonstrated that the amplitude of the conductance oscillations in the ballistic regime is determined by the value of the noncompensated spin localized in the ring. The results are in agreement with the concept of fractional quantization of the ballistic conductance, proposed by us earlier [Phys. Rev. B71, 113311 (2005)].Published versio

Electron — positron quantum droplets

A new physical object, electron-positron quantum droplet, is suggested. Structure, stability and dynamics of such objects are discussed. The analysis is based on the non-relativistic self-consistent local-density approximation. An essential role of many-body effects in the formation of the droplets is demonstrated. Their properties are compared with the known physical objects such as metal clusters and clusters of excitons in a solid.

QUANTUM-MECHANICAL MODELING OF SPATIAL AND BAND STRUCTURE OF Y3AL5O12 SCINTILLATION CRYSTAL

Spatial and electronic structures of a unit cell of yttrium-aluminum garnet have been studied. Quantum-mechanical model have been presented. Semi-empirical methods PM6 and PM7 have been used for geometry optimization of the crystal unit cell. Band structure has been calculated within density functional theory with the use of PBE exchange-correlation functional. Histograms of metal-oxygen distances for equilibrium geometry have been constructed. Comparison of the used methods has been carried out and recommendation about their applicability for such problems was given. The single-particle wave functions and energies have been calculated. The bandgap was estimated. The band structure was plotted. It was shown that the method gives reliable results for spatial and band structure of Y3Al5O12 scintillation crystal. The results of this work can be used for improvement of characteristics of garnet scintillation crystals