Hayk Sarkisyan

Russian - Armenian (Slavonic) University

The current work used the effective mass approximation conjoined with the finite element method to study the exciton states in a conical GaAs quantum dot. In particular, the dependence of the exciton energy on the geometrical parameters of a conical quantum dot has been studied. Once the one-particle eigenvalue equations have been solved, both for...

One of the promising areas of research applicable in astrophysics is the study of the properties of quantum dots (QDs) and quantum wells (QWs) in the IR region of the spectrum. The IR region of the spectrum contains a huge amount of astronomical information. Devices based on GaAs/AlGaAs QWs and Ge/Si QDs can serve as detectors and sources of IR rad...

One of the promising areas of research applicable in astrophysics is the study of the properties of quantum dots (QDs) and quantum wells (QWs) in the IR region of the spectrum. The IR region of the spectrum contains a huge amount of astronomical information. Devices based on GaAs/AlGaAs QWs and Ge/Si QDs can serve as detectors and sources of IR rad...

The exciton states and their influence on the optical absorption spectrum of CdSe and PbS nanoplatelets (NPLs) are considered theoretically in this paper. The problem is discussed in cases of strong, intermediate, and weak size quantization regimes of charge carrier motion in NPLs. For each size quantization regime, the corresponding potential that...

A review of the results of studies of terahertz radiation associated with impurity electron transitions in n-doped GaAs/AlGaAs quantum wells under conditions of interband optical excitation of nonequilibrium charge carriers is presented. The principles of radiation generation and methods of controlling its intensity are described: a decrease in the...

We briefly review the analysis of the energy spectrum, the envelope eigenfunctions of electron, hole and exciton states, and the direct interband light absorption in cone-shaped and spheroidal impenetrable quantum dots. We apply high-order finite element method and calculation schemes of Kantorovich method in comparison with the adiabatic approxima...

The results of comprehensive studies of near-infrared photoluminescence and mid-infrared equilibrium and photoinduced absorption spectra in structures with Ge/Si quantum dots with different doping levels at different optical pumping intensities and different temperatures are presented. Obtained dependences of interband photoluminescence spectra on...

We have presented a theoretical investigation of exciton and biexciton states for the ground and excited levels in a strongly oblate ellipsoidal quantum dot made from GaAs. The variational trial wave functions for the ground and excited states of the exciton and biexciton are constructed on the base of one-particle wave functions. The energies for...

The heating of electrons under longitudinal optical phonon scattering in a triangular GaN/AlGaN quantum well was studied theoretically. The energy loss rate of electrons was calculated in consideration of the dynamical screening and the hot phonon effect. The dependence of the electron temperature on the longitudinal electric field was calculated....

The theoretical investigation of interband and intraband transitions in an asymmetric biconvex lens-shaped quantum dot are considered in the presence of an external magnetic field. The selection rules for intraband transitions are obtained. The behaviors of linear and nonlinear absorption and photoluminescence spectra are observed for different tem...

Linear and nonlinear optical properties in colloidal CdSe/CdS core/shell quantum dots with different sizes have been theoretically investigated in the framework of effective mass approximation. The electron states in colloidal CdSe/CdS core/shell quantum dots have been calculated using the finite element method. The intraband linear and nonlinear a...

In the framework of the adiabatic approximation strongly prolate and oblate conical quantum dots in the external electric field have been investigated. Analytical expressions for the particle wave function and energy spectrum are obtained for both cases. The dependencies of the absorption edge on the geometrical parameters and external field streng...

By using the numerical discretization method within the effective-mass approximation, we have theoretically investigated the exciton-related Raman scattering, interband absorption and photoluminescence in colloidal CdSe/CdS core/shell quantum dots ensemble. The interband optical absorption and photoluminescence spectra have been revealed for CdSe/C...

The theoretical investigation of linear and third-order nonlinear absorption coefficients and refractive index changes in the cylindrical quantum dot with two models of confinement potentials in axial direction, namely, modified Pöschl-Teller and Morse potentials, and parabolic potential in radial direction, have been considered in the presence of...

The theoretical investigation of strongly prolate conical quantum dot with infinite confinement potential in presence of external axial electric field has been considered. The analytical form of energy of spectra and wavefunctions has been calculated. The selection rules for interband transitions have been obtained. The linear interband absorption...

In this paper, the behavior of the few-electron gas localized in a strongly prolate ellipsoidal quantum dot has been investigated. It is shown that, due to the specific geometry of the quantum dot, the motion of particles in the considered system can be separated into fast and slow subsystems. “Moshinsky atom” model has been chosen as interacting p...

In this paper, the behavior of a heavy hole gas in a strongly prolate ellipsoidal Ge/Si quantum dot has been investigated. Due to the specific geometry of the quantum dot, the interaction between holes is considered one-dimensional. Based on the adiabatic approximation, it is shown that in the z-direction, hole gas is localized in a one-dimensional...

This chapter presents the results of a theoretical study of single-electron, two-electron, and impurity states as well as interband optical absorption and single-electron current in spherical and cylindrical core/shell quantum dots. Analytically exact solvable models of the confining potentials of core/shell quantum dots are discussed.

We study theoretically the quantum states of two interacting excitons in coaxial double quantum rings. An interplay between exciton–exciton Coulomb interactions and specific geometry of the structure leads to the emergence of peculiar energy spectrum of two exciton system. We develop a semi-analytic approach providing highly accurate energies of sy...

This article discusses specific quantum transitions in a few-particle hole gas, localized in a strongly oblate lens-shaped quantum dot. Based on the adiabatic method, the possibility of realizing the generalized Kohn theorem in such a system is shown. The criteria for the implementation of this theorem in a lens-shaped quantum dot, fulfilled in the...

Electronic states are considered in a cylindrical quantum dot with the Kratzer confining potential in the axial direction. In this system, the nonlinear optical rectification and second harmonic generation for intraband transitions are studied theoretically. Analytical expressions are calculated for the energy spectrum of the wave functions, as wel...

The biexciton, negative and positive trion states in strongly oblate ellipsoidal quantum dot are investigated in the framework of variational method and Heisenberg's uncertainty principle. Because of the oblate geometry of the quantum dot, the exciton complexes are considered as quasi-two-dimensional. The trial wave function for the biexciton and t...

One-electron states in a toroidal quantum dot in the presence of an external magnetic field have been considered. The magnetic field operator and the Schrodinger equation have been written in toroidal coordinates. The dependence of one-electron energy spectrum and wave function on the geometrical parameters of a toroidal quantum dot and magnetic fi...

The experimental and theoretical results of studies of optical absorption in doped Ge/Si quantumdot structures in the far-infrared region, corresponding to the energies of transitions of holes from the ground state to the lowest excited size-quantization state, are reported. An analytical theory of the size quantization of holes in a lens-shaped qu...

One electron and exciton states in toroidal quantum dot (QD) have been considered. The convenient coordinate system has been defined and the Schrodinger equation has been solved in these coordinates. The electron energy spectrum and wave function dependence on the geometrical parameters of toroidal QD have been obtained. The comparison with the res...

Hydrogen-like donor impurity states in strongly oblate ellipsoidal quantum dot have been studied. The hydrogen-like donor impurity states are investigated within the framework of variational method. The trial wave function constructed on the base of wave functions of the system without impurity. The dependence of the energy and binding energy for t...

In this paper, the behavior of the few-body electron gas localized in a strongly prolate ellipsoidal quantum dot with the presence of the uniform external magnetic field has been investigated. Due to the specific geometry of the quantum dot it has been shown that the motion of the particles in the considered system can be separated into fast and sl...

The problem of the features of the electron energy spectrum in a quantum parallelepiped has been considered. The family of triply degenerate energy levels has been found for the chosen model of the quantum parallelepiped. The optical transitions in this system has been investigated. It has been established that primitive Pythagorean triples are in...

The electronic, optical and electrostatic properties of the spherical core/shell/shell quantum nanolayer with an off-centered impurity have been studied. Spherical nanolayers of both “small” and “large” radii have been considered in the framework of perturbation theory and the variational method. Photoionization cross-section that corresponds to th...

The electronic states in a conical quantum dot in the framework of the adiabatic approximation as well as the combined approach with the perturbation theory have been considered. The obtained results have been compared with the results of numerical methods–the finite element and the Arnoldi methods. The interpolation formula for the energy correcti...

The problem of electromagnetic absorption in the electronic gas, which is localized in asymmetric biconvex thin quantum lens, is discussed. It is shown, that in the case of thin lens, in the plane of quantum lens electron gas is localized in two-dimensional parabolic confining potential. Thus, in this system the conditions for the realization of th...

Diamagnetic properties of the electron gas in a cylindrical quantum dot with parabolic confinement potential have been investigated. The analytical expressions have been obtained for mean energy, mean magnetization and mean magnetic susceptibility of the electron gas. The diamagnetic character of such system has been shown.

In the framework of the adiabatic approximation, the energy states of electron, as well as the direct light absorption are investigated in conical quantum dot under the external magnetic field. Analytical expressions for the particle wave function and energy spectrum are obtained. The dependence of the absorption edge on the geometrical parameters...

Diamagnetic properties of the electron gas in cylindrical nanolayer have been investigated. The dependence of mean energy, mean magnetization and mean magnetic susceptibility on the values of magnetic field is obtained. Comparison of these dependencies with the case, when the electron gas is localized in the cylindrical quantum dot, is carried out....

Two-electron states in a spherical QD with the hydrogenic impurity located in the center and with a finite height confinement potential barrier are investigated. The effective mass mismatch have been taken into account. The dependence of ground state energy and Coulomb electron-electron interaction energy correction on the QD size is studied. The p...

In this paper, on the basis of the geometric adiabaticity the problem of magnetoabsorption of few-body electron gas, localized in strongly prolate ellipsoidal quantum dot, has been investigated. Initially the confinement potential of the quantum dot was considered as rectangular and impenetrable. Due to the specific geometry of the quantum dot has...

The problem of definition and control of electrostatic field, created by electron, localized in cylindrical nanolayer from InSb is considered. The average values of quadrupole and dipole moments have been calculated and the appropriate corrections in the potential and the electric field strength have been found. The obtained results can be applied...

The ICTP smr2633: 2nd International Symposium "Optics and its Applications" (OPTICS-2014) http://indico.ictp.it/event/a13253/ was held in Yerevan and Ashtarak, Armenia, on 1-5 September 2014. The Symposium was organized by the Abdus Salam International Center for Theoretical Physics (ICTP) with the collaboration of the SPIE Armenian Student Chapter...

In the framework of the adiabatic approximation, the energy states of electron as well as the direct light absorption are investigated in conical quantum dot. Analytical expressions for particle energy spectrum are obtained. The dependence of the absorption edge on geometrical parameters of conical quantum dot is obtained. Selection rules are revea...

One-electron states in narrow-band spherical InSb nanolayer are considered. Electron dispersion law is described in double-gap Kane model, when electrons and light holes behaviors are described by Klein–Gordon equation analog. On the basis of derived expressions for one particle wave functions, dipole and quadrupole electron moments in above mentio...

Two-electron impurity states in parabolic confinement have been investigated. We have estimated the ground-state energy value, using the Heisenberg uncertainty relation. Using variational methods the ground state energy and wave function of the single-electron impurity problem have been achieved. The dependence of ground-state energy and Coulomb el...

An exactly solvable problem of impurity states is considered in core/shell/shell spherical quantum dot. Kratzer molecular potential is taken for confinement potential. The analytical expressions are obtained for the energy spectrum and wave functions of the impurity electron. The dependencies of the total energy and the binding energy of the impuri...

The electronic states as well as interband and intraband electrooptical transitions are considered for the narrow gap InSb nanotube in the field of homogeneously charged ring. The problem is solved in the framework of the variational approach. The field of the charged ring is brought to the field of the modified one dimensional Coulomb-like potenti...

Current of the spin magnetic moment of an electron coupled with hydrogen-like impurity, placed in the center of a spherical quantum dot, is studied. Confinement potential of the quantum dot is approximated by rectangular infinitely high walls. S-states of electron for both positive and negative values of total energy are considered. Dependences of...

The exactly solvable model of quasi-conical quantum dot, having a form of spherical sector is proposed. Due to the specific symmetry of the problem the separation of variables in spherical coordinates is possible in the one-electron Schrodinger equation. Analytical expressions for wave function and energy spectrum are obtained. It is shown that at...

Using the Heisenberg uncertainty relationship and the stationary perturbation theory we consider two-electron states in a spherically symmetric parabolic quantum dot (parabolic helium atom). The dependence of ground-state energy on the QD size is studied. The energy of two-electron system monotonically decreases with QD radius increase. The problem...

An analytical solution of the quantum problem of an electron on a spherical segment with angular confinement potential in the form of rectangular impenetrable walls is presented. It is shown that the problem is reduced to finding solution of hypergeometric equation. On the basis of the obtained results the optical interband transitions in this syst...

A quantum model of the Thomson helium atom is considered within the framework of stationary perturbation theory. It is shown that from a formal point of view this problem is similar to that of two-electron states in a parabolic quantum dot. The ground state energy of the quantum Thomson helium atom is estimated on the basis of Heisenberg's uncertai...

Two electron states in a quantum ring on a spherical surface are discussed. The problem is discussed within the frameworks of Russell-Saunders coupling scheme, that is, the spin-orbit coupling is neglected. Treating Coulomb interaction as a perturbation, the energy correction for different states is calculated. The dependence of the Coulomb interac...

The states of charge carriers in a narrow-gap semiconductor InSb film, placed in a uniform electrostatic field, are considered theoretically. We consider the case when the heavy holes are described by the standard dispersion, and Kane’s dispersion law takes place for electrons and for light holes within the framework of two-band mirror model. For a...

An analytical solution of the quantum problem of an electron on a spherical segment with angular confinement potential of the form of rectangular impenetrable walls is presented. It is shown that the problem is reduced to finding solution of hypergeometric equation. As an application of the obtained results the quantum transitions in this system ar...

Densities of persistent orbital and spin magnetic moment currents of an electron in a cylindrical nanolayer in the presence of external axial magnetic ?eld are considered. For the mentioned current densities analytical expressions are obtained. The conditions when in the system only spin magnetic moment current is present are de?ned. Dependencies o...

An electron gas in a strongly oblated ellipsoidal quantum dot with impenetrable walls is considered. Influence of the walls of the quantum dot is assumed to be so strong in the direction of the minor axis (the OZ axis) that the Coulomb interaction between electrons in this direction can be neglected and considered as two-dimensional, coupled. On th...

In the effective mass approximation for electronic (hole) states of a spheroidal quantum dot with and without external fields the perturbation theory schemes are constructed in the framework of the Kantorovich and adiabatic methods. The eigenvalues and eigenfunctions of the problem, obtained in both analytical and numerical forms, were applied for...

In the framework of effective mass approximation and in strong size quantization regime the absorption coefficients for ensembles of spheroidal quantum dots (SQDs) are analyzed using the eigenvalues and eigenfunctions, calculated by means of Kantorovich and adiabatic methods. The comparison of absorption coefficients for oblate and prolate SQDs wit...

Two electron states in a thin spherical nanolayer are discussed. Adiabatic approach is used to divide the system to fast (radial) and slow (angular) subsystems. This leads the Coulomb interaction to be dependent on angular variables, more precisely, on the relative angle between electrons. Approximated Coulomb interaction potential is discussed. An...

In this work the interband optical absorption and Stark shift in the ensemble of InSb spherical quantum layers are investigated. Calculations are carried out both for the cases of parabolic and Kane's dispersion laws. The distribution of layers by their inner radii is taken into account. The effect of weak electric field on the energy levels coupli...

Optical properties of a nanoring with Winternitz-Smorodinsky confinement potential in the presence of an external magnetic field have been studied theoretically. Our results demonstrate that energy, oscillator strength and the linear, nonlinear and total absorption are strongly affected by size of the nanoring. Also, we found that magnetic field ha...

InSb has been utilized for many purposes due to the properties just described. Because of low electron effective mass and the resulting large-electron mobility, InSb can be used for very high-speed electronic devices and is being used in magneto-resistive sensor in the automotive industry. High-performance InSb detectors have been fabricated with t...

PREFACE The papers selected for this volume were reported at the International Symposium ‘Optics and its applications’ (OPTICS-2011, Yerevan & Ashtarak, Armenia, September 5–9, 2011), http://www.ipr.sci.am/optics2011/. The Symposium was organized by the SPIE Armenian Student Chapter and major Armenian R&D organizations, universities and industrial...

In this paper for one electron states dipole and quadrupole moments are studied in spherical impenetrable quantum nanolayer. It is shown that dipole moment is zero for the considered system. An analytical formula for quadrupole moment is derived. Quadrupole moment dependence upon one radius of the nanolayer, when the other one is fixed, is obtained...

The impurity states in quantum dot with parabolic confinement were studied in adiabatic approximation. The analytical expressions for the energy of ground and excited states were obtained. It was shown, that the influence of walls results in raising the ground energy level.

The absorption of light in ellipsoidal quantum dot in the presence of a magnetic field is discussed using perturbation theory. Also the same problem is discussed using the normal modes. Quantum dot absorption coefficient is calculated - as well as threshold frequency of absorption - as a function of applied magnetic field. Theoretical results are c...

On the example of InSb we consider the influence of a strong homogeneous electrostatic field on the state of carriers in a narrow-band quantized cylindrical layer in the case of Kaine dispersion law. Explicit expressions for the energy spectrum and wave function envelopes of charge carriers in the heterolayer are obtained. It is shown that under ac...

Direct optical absorption of light in cylindrical quantum dot was theoretically investigated. Analytical expressions for light absorption coefficients were found for two regimes of size quantization: strong and weak. The corresponding selection rules for optical transitions are defined. The expressions for absorption threshold frequencies are found...

In this article, we investigate an exactly solvable model, describing the behavior of electrons in a cylindrical quantum dot GaAs/Ga1-xAlxAs with parabolic confinement potential under the influence of external electrical and magnetic fields, directed along the axes of the cylinder. The wave-function and energy levels of the electron are found. An e...

We have studied the nonlinear optical absorption and the nonlinear optical rectification of an exciton in a nanoring in the presence of magnetic flux. The calculation results show that one can control the properties of nonlinear optical absorption and nonlinear optical rectification of a nanoring by tuning the outer and inner radius. Moreover, we f...

Two electronic states in impenetrable spherical quantum nanolayer are discussed. The Coulomb interaction between the electrons is considered as perturbation. The problem is discussed within the frameworks of Russell–Saunders coupling scheme, that is, the spin–orbit interaction is neglected. For this system the analogue of helium atom theory is repr...