Kuchak A. Spectral parameters of quasiparticles in semiconductor nanotubes and nanorings

In the thesis, the energy spectra and interaction of quasiparticles (electrons, holes, excitons) with each other, impurity and external electric and magnetic fields are theoretically studied in multilayered semiconductor closed and open nanotubes and nanorings. All calculations are performed in the model of effective masses and rectangular potentials. Theoretical model for studying the interaction of an electron with a donor impurity located on the axial axis of closed multilayered cylindrical nanotube is developed. The dependences of the electron-impurity binding energy, the complete electron energy and the oscillator strengths of the intra-band quantum transitions on the inner wire radius and the thickness of the multilayered nanotube are analyzed. All these dependences are complicated and non-monotonous, due to the complicated nature of the density distribution of the probability of location of electron which is interacting with impurity in nanotube. The theory of quasi-stationary electron and hole states in a multilayered open cylindrical semiconductor nanotube is developed. The dependences of the resonant energies and the widths of the electron, hole, and exciton on the thickness of the multilayered open cylindrical nanotube are analyzed. It is shown that both resonant energies and electron or hole widths non-monotonously depend on the thickness of the nanotube. In the dependences of the resonance energies, it is manifested in the form of alternating horizontal and descending regions while in the dependence of the resonance widths the bright maxima are observed in the regions of small values. The influence of the magnetic field on the energy spectrum of the electron and the oscillator strengths of the intra-band quantum transitions in double semiconductor quantum nanorings are investigated. The dependences of the electron energies and oscillator strengths of intra-band quantum transitions on the magnitude of magnetic field induction are analyzed. It is shown that in the magnetic field, the degeneration of the energy spectrum of an electron over the magnetic quantum number, which takes place in an arbitrary cylindrical nanostructure in the absence of a field, is taken off. The ground state of the electron in double nanorings, depending on the magnitude of the magnetic field induction, periodically become the states with negative quantum numbers. This feature is a manifestation of the Aaron-Bohm effect. The influence of a constant electric field on the energy spectrum of the electron and oscillator strengths of intra-band quantum transitions in double semiconductor quantum nanorings is investigated. The dependences of the electron energies and the oscillator strengths of intra-band quantum transitions on the electric field intensity are analyzed. It is shown that the electric field significantly changes the density distribution of the probability of quasiparticle location in nanostructure while the electron energies and the oscillator strengths strongly depend on the magnitude of the intensity. Keywords: multilayered cylindrical nanotube, double quantum rings, donor impurity, energy spectrum, oscillator strengths, electric field, magnetic field.