arXiv subjects

O. I. Hryhorchak

Publications and source records attributed to O. I. Hryhorchak.

12 recordsLinked to original sources

arXiv2020

Finite periodic $δ-δ'$ comb

A finit periodic $δ-δ'$ comb was solved by the help of both classical approach based on a direct solving of a Sr\"{odinger} equation and a quantum wave impedance method. It was demonstrated that the violation of a periodicity leads to the formation of energy levels in band gaps. The expresion for a surface levels (Tamm's levels) were found in this model system. Obtained results allow extending the scope of theoretical models which are applicable for a describing real quantum mechanical systems as well as better understanding the physical properties of systems in which the boundary dependent states are involved, especially the influence of boundary dependent electronic states on the physical properties of low-dimensional systems.

quant-ph↗

arXiv2020

Application of a quantum wave impedance approach for a quantum capacitance calculation

A method for a calculation of quantum capacitance for a two-dimesional electron gas (2DEG) in potential wells of complicated geometry on the base of a quantum wave impedance technique was proposed. The application of this method was illustated on four different forms of potential wells: infinite and finit rectangular well, a finit rectangular double well and a parabolic double well. It was shown how a quantum capacitance of these wells depends on its parametres. Numerical calculations of a quantum capacitance for mentioned potential wells were made at temperature $T=0$ and the results were presented graphically.

quant-ph↗

arXiv2020

An application of a quantum wave impedance method to finite periodic structures

The relations between a quantum wave impedance function and elements of transfer and scattering matrixes for quantum mechanical systems with arbitrary localized form of potential were established. Obtained results allows using the advantages of both methods, namely a transfer matrix technique and a quantum wave impedance approach, for an investigating of nanosystems with a complicated geometry of a potential. A finit Dirac comb was solved and expressions for Tamm's levels in this system were derived within both approaches.

quant-ph↗

arXiv2020

Analytical representation of an iterative formula for a quantum wave impedance determination in a case of a piecewise constant potential

An analytical solution for a quantum wave impedance in a case of piesewise constant potential was derived. It is in fact an analytical depiction of a well-known iterative method of a quantum wave impedance determination. The expression for a transmission probability as a function of a particle energy for an arbitrary cascad of constant potentials was obtained. The application of obtained results was illustrated on a system of double-well/barrier structures.

quant-ph↗

arXiv2020

Effective technique of numerical investigation of systems with complicated geometry of a potential

We have developed the technique of a quantum wave impedance determination for the sequence of not only constant potentials but also for potentials of forms for which the solution of a Shrödinger equation exists at least in terms of special functions. The method was applied for a deformed double-barrier system and as a result the dependence of a transmission probability $T$ on an energy $E$ of a particle at different parameters of this system was numerically calculated. Obtained results can be applied to the numerical investigation of a quantum mechanical systems with complicated geometry (spatial structure) of a potential.

quant-ph↗

arXiv2020

Numerical study of quantum mechanical systems using a quantum wave impedance approach

The approximate numerical method for a calculation of a quantum wave impedance in a case of a potential energy with a complicated spatial structure is considered. It was proved that the approximation of a real potential by a piesewise constant function is also reasonable in a case of using a quantum impedance approach.The dependence of an accuracy of numerical calculations on a number of cascads by which a real potential is represented was found. The method of including into a consideration of zero-range singular potentials was developed.

quant-ph↗

arXiv2020

Application of a quantum wave impedance method for study of infinite and semi-infinite periodic media

This paper is dedicated to an application of a quantum wave impedance approach for a study of infinite and semi-infinite periodic systems. Both a Dirac comb and a $δ-δ'$ comb as well as a Kronig-Penney model are considered. It was shown how to reformulate the problem of an investigation of mentioned systems in terms of a quantum wave impedance and it was demonstrated how much a quantum wave impedance approach simplifies studying these systems compared to other methods. The illustation of such a simplification was provided by application of classical approach, transfer matrix technique and a quatum wave impedance method for solving Kronig-Penney model.

quant-ph↗

arXiv2020

Application of a quantum wave impedance method for zero-range singular potentials

An application of a quantum wave impedance method for a study of quantum-mechanical systems which con\-tain singular zero-range potentials is considered. It was shown how to reformulate the problem of an investigation of mentioned systems in terms of a quantum wave impedance. As a result both the scattering and bound states problems are solved for systems of single $δ$, double $δ$ and single $δ-δ'$ potentials. The formalization of solving systems with an arbitrary combination of a piesewise constant potential and a $δ$-potentials with the help of a quantum wave impedance approach is described.

quant-ph↗

arXiv2020

Quantum wave impedance calculation for an arbitrary piesewise constant potential

The method of a determination of a quantum wave impedance for an arbitrary piecewise constant potential was developed. On the base of this method both the well-known iterative formula \cite{Khondker_Khan_Anwar:1988} and alternative ways for a quantum wave impedance calculation were derived. A scattering and a bound state case were considered. The general form of a wave function of bound states for an arbitrary piesewise constant potential was obtained as well as transmission and reflection coefficients in a scattering case. The applying of method was demonstarted on the system of double well/barrier.

quant-ph↗

arXiv2020

Reformulation of a transmission and reflection problems in terms of a quantum wave impedance function

On the base of a 1D Shrödinger equation the non-linear first-order differential equation (Ricatti type) for a quantum wave impedance function was derived. The advantages of this approach were discussed and demonstrated for a case of a single rectangular barrier. Both the scattering and the bound states problem were reformulated in terms of a quantum wave impedance and its application for solving both these problems was considered. The expressions for a reflection and a transmission coefficient were found on the base of a quantum wave impedance approach.

quant-ph↗

arXiv2020

An application of a quantum wave impedance approach for solving a nonsymmetric single well problem

A short introduction of a relation between a Green's function and a quantum wave impedance function as well as its application to a determination of eigenenergies and eigenfunctions of a quatum-mechanical system is provided. Three different approaches, namely a classical approach based on a direct solving of a Shrödinger equation, a transfer matrix method and a quantum wave impedance technique, for a calculation of eigenenergies and eigenfunctions of a quantum mechanical nonsymmetric single well system are considered. A comparision of these approaches gives the possibility to clarify advantages and drawbacks of each method which is useful especially for teaching and learning purposes.

quant-ph↗

arXiv2015

First sound velocity in liquid $^{4}$He

Based on the many-boson system structure factor, which takes into account three- and four-particle direct correlations, there was found the first sound velocity temperature behaviour in liquid $^4$He in the post-RPA approximation. The expression received for the sound velocity matches with the well-known results in both low and high temperature limits. The results of this paper can be used to analyze the contributions of three- and four-particle correlations into thermodynamic and structural features of liquid $^4$He.

cond-mat.quant-gas↗