Перегляд за Автор "Korol, Anatoliy"

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Conductivity of the junction: d-wave pairing superconductive graphene — normal graphene with different Fermi velocity
(2018) Korol, Anatoliy; Medved, Nataliya; Vyshniak, Volodymyr; Litvynchuk (Vorontsova), Svitlana
In recent years, much attention has been paid to the study of graphene and various graphene-based structures. This is due to non-trivial properties of graphene, such as a linear dispersion law for the quasi-particles, whose behavior at low energies is described by an equation similar to the DiracWeyl one, unusual quantum Hall effect, the property of chirality, the Klein tunneling, high mobility, ballistic transport etc. [1, 2]. It should also be borne in mind that graphene is a promising material in modern electronics in terms of replacing the silicon technology, the development of which has reached its limit, for the graphene one. One of the priority directions is to study the various possibilities of controlling the energy spectrum of the graphene-based structures.
Dielectric permittivity of semiconductors with narrow forbidden gap in the long-wave limit
(1976) Sheka, D.; Korol, Anatoliy; Шека, Д. І.; Король, Анатолій Миколайович
In the random phase approximation the dielectric permittivity is evaluated for a semiconductor with a band structure described by Kane’s energy band scheme. It is demonstrated that the fact that several hole bands have been taken into account, when the operator of the kinetic energy ceased to be the Dirac one plays the principal role in the calculation of the static dielectric permittivity ε(q →0).
Effect of deep impurity levels on Schottky barrier diode characteristics
(1975) Korol, Anatoliy; Kitsai, M. Ye.; Strikha, V.; Sheka, D.
In the presence of an arbitrary number of deep donor levels volt-ampere and volt-farad characteristics are obtained for the Schottky barrier diode which contains a thin dielectric layer between the metal and the semiconductor.
Energy spectra of the fibonacci graphene superlattice
(2013) Korol, Anatoliy; Isai, Valeriy
Energy spectra of the graphene-based Fibonacci superlattice (SL) in the presence of the forbidden band in graphene have been investigated.
Energy spectra of the Fibonacci superlattice based on the gapped Graphene
(2013) Korol, Anatoliy; Isai, Valeriy
Energetical spectra for the Fibonacci superlattice on the gapped grapheme are evaluated andanalyzed.
Energy Spectra of the Graphene-based Fibonacci Superlattice Modulated by the Fermi Velocity Barriers
(2016) Korol, Anatoliy; Litvynchuk (Vorontsova), Svitlana; Baglyuk, Sergey; Isai, Valeriy
The energy spectra of the Weyl-Dirac quasi-electrons for this SL are calculated with the help of the transfer matrix method in the continuum model. The Fibonacci quasi-periodic modulation in graphene superlattices with the velocity barriers can be effectively realized by virtue of a difference in the velocity barrier values.
Energy spectrum of a hierarchical superlattice with impurities in potential barriers
(1994) Korol, Anatoliy
A 1D superlattice in which a hierarchical modulation of the potential is caused by impurity centers in potential barriers is discussed. A transfer-matrix method is used to calculate and analyze the tunneling spectra of this hierarchical superlattice.
Kinetics of the early growth of actinomycete streptomyces coelicolor
(1989) Kotov, V.; Korol, Anatoliy
Various growth characteristics of Streptomyces coelicolor are considered and numerous relations among them are discussed. An attempt is made to tie the events at the hyphal level to an understanding of phenomena at the organism level. The results are presented as corollaries of a theoretical model based on a special atochastic branching process involving apices of three types. Theoretical conclusions are compared to the experimental data on growth and branching of colonies of S.coelicolor from paper.
Novel version of the Fibonacci superlattices formed of grapheme nanoribbons: Transmission spectra
(2017) Korol, Anatoliy; Litvynchuk (Vorontsova), Svitlana
The energy spectra of a novel version of graphene-based Fibonacci superlattices (SL) are calculated. Anew quasiperiodical factor is considered. The SL is built of grapheme nanoribbons and the quasi-periodicity is formed due to the fact that different ribbons are used as individual of the SL and are placed along the lattice growth axis in accordance with the Fibonacci inflation rule. the SL is com posed of smooth-edges and a metal-like armchair NR, and we propose to use a metal-like and a semiconductor armchair NR for another case. Розраховано енергетичні спектри новітньої версії графенових надграток (НГ) Фібоначчі. Розглядається новий квазіперіодичний чинник. НГ побудована із графенових нанострічок, а квазіперіодичність утворюється завдяки тому, що різні стрічки, які використовуються як індивідуальні елементи НГ, розміщено вздовж осі вирощування згідно з інфляційним правилом Фібоначчі. В одному випадку НГ сформовано із стрічок і гладкими краями і металоподібних крісло подібних стрічок, і ми пропонуємо використати металоподібні і напівпровідникові кріслоподібні стрічки в іншому випадку.
On transport parameters of a mesoscopic crystal with impurities at potential barriers
(1996) Korol, Anatoliy
A one-dimensional ballistic superlattic (mesoscopic crystal) containing impurity centers at potential barriers is considered. The dependence of the transmission coefficient T on the energy ε is evaluated for this structure. It is shown that scatterers are responsible for an increase in T by several orders of magnitude. Розглядається одновимірна балістична надгратка (мезоскопічний кристал), що містить домішки в потенціальних бар’єрах. Обчислена залежність коефіцієнта трансмісії Т від енергії ε. Показано, що завдяки розсіювачам величина Т збільшується на декілька порядків.
Peculiarities of the motion of the pseudorelativistic Dirac quasiparticles in the alpha-T3 model with the step-like barrier
(2020) Korol, Anatoliy; Medved, Nataliya
Within the continuous approach, the transmission coefficient T of the Dirac quasielectrons through a step-like potential barrier in the a-T3 model is calculated and analyzed. It is believed that the degree of coupling of the central atom with the atoms in the vertices of the hexagonal lattice is characterized by the parameter a, which can acquire values from zero to one. Particular attention is given in the work to intermediate values of a, since, it is known from the literature, that they are important for observing a lot of physical phenomena. The wave functions as well as the transmission ratio are sought by the Dirac type equation. The Hamiltonian of the system is represented by a spinor of 9 components, which is expressed, in particular, by the parameter a The transmission coefficient is found by means of matching of wave ftmctions at heterojunctions. In particular, it is found that there is a range of problem parameters, such as the height of the electrostatic barrier U, the energy of the quasielectrons E, the ratio of the Fermi velocities in the barrier and out-of-barrier areas (3, in which the value of the transmission coefficient reaches maximum, that is, it is close to unity for a values close to unity. In this area, the dependence of the transmission coefficient on the value of a is weak. When the value of a becomes exactly equal to one, then the value of the transparency coefficient reaches the absolute maximum, that is, one. For the zero angle of incidence of quasiparticles on the barrier, the Klein paradox phenomenon is observed, i.e, the quantum transparency of the system is perfect, and this is right for any values of the parameters a, (3, U, E. For certain ratios of particle energy E, the barrier height U and the magnitude of p there is the supertunneling phenomenon, which is that under these conditions the transmission coefficient is equal to one independently of the angle of incidence of the particles on the barrier. Characteristic of the transmission spectra T(E) is also the presence of a critical angle of incidence and a gap of energies. У рамках континуального підходу розраховано і проаналізовано коефіцієнт трансмісії Т діраківських квазіелектронів крізь сходинкоподібний потенціальний бар’єр в а-Тз моделі. Вважається, що ступінь зв’язку центрального атома з атомами у вершинах гексагональної гратки характеризується параметром а, який може набувати значення від нуля до одиниці. Особливу увагу приділено проміжним значенням а, оскільки, як відомо з літератури, вони є важливими для спостереження низки фізичних явищ. Хвильові функції, а також коефіцієнт трансмісії визначено за допомогою рівняння діраківського типу. Гамільтоніан системи представлено спінором із дев ’яти компонентів, які виражаються, зокрема, через параметр а. Коефіцієнт трансмісії знайдено за допомогою зшивання хвильових функцій на гетеромежах. З ’ясовано, зокрема, що існує область параметрів задачі, таких як висота електростатичного бар ’єру U, енергія квазіелектрона Е, відношення швидкостей Фермі в бар ’єрній і позабар ’єрній областях Д в якій значення коефіцієнта трансмісії досягає максимуму, тобто наближається до одиниці, для близьких до одиниці значень а. В цій області залежність коефіцієнта трансмісії від величини а є слабкою. Коли величина а стає точно рівною одиниці, то і значення коефіцієнта прозорості досягає абсолютного максимуму, тобто одиниці. Для нульового кута падіння квазічастинок на бар ’єр спостерігається явище клей- нівського парадоксу, тобто квантова прозорість системи є ідеальною, і це справедливо для будь-яких значень параметрів а, Д, U, Е. Для певних співвідношень енергії частинок Е, висоти бар’єру U і величини Д має місце явище супертунелювання, яке полягає в тому, що для заданих умов коефіцієнт трансмісії дорівнює одиниці незалежно від кута падіння частинок на бар’єр. Характерніш для трансмісійних спектрів Т(Е) є також наявність критичного кута падіння та забороненої зони енергій.
The effect of both abrupt and strong enhancement of current in the semiconductor system : Schottky barrier containing a double barrier resonant-tunneling structure
(2001) Korol, Anatoliy; Tretyak, O.; Sheka, D.
The current-voltage characteristics for the double barrier resonant-tunneling structure incorporated into the depletion region of a Schottky barrier, are evaluated and analyzed. Hence both a very sharp and strong enhancement of current through the structure considered takes place for forward bias.
The energy spectra of the graphene-based quasi-periodic superlattice
(2018) Korol, Anatoliy; Sokolenko, Anatoly; Sokolenko, Igor
The spectra of the Dirac quasielectrons transmission through the Fibonacci quasi-periodical superlattice (SL) are calculated and analyzed in the continuum model with the help of the transfer matrix method. The one-dimensional SL based on a monolayer graphene modulated by the Fermi velocity barriers is studied. A new quasi-periodical factor is proposed to be considered.
The sharply nonlinear current – voltage characteristic of a structure with a quantum well built in the depletion region of a Schottky barrier
(2012) Korol, Anatoliy; Nosenko, I.
The heterostructure in which a quantum well is formed in the depletion region of the Schottky barrer is considered. The forward current – voltage characteristic of this structure is evaluated and analyzed.
Transmission of the relativistic fermions with the pseudospin equal to one through the quasiperiodic barriers
(2018) Korol, Anatoliy; Medved, Nataliya; Sokolenko, Anatoly
The focus of this work is to explore quasiparticle transmission through the quasi-periodic superlattices based on the Lieb lattice, in which the fermions pseudospin equals to one. We are the first to calculate and analyze the transmission spectra for such structures. Дана робота фокусується на дослідженні трансмісії квазічастинок крізь квазіперіодичні надгратки, основані на гратці Ліба, в якій псевдоспінферміонів дорівнює одиниці. В роботі вперше розраховуються і аналізуються трансмісійні спектри для даних структур.
Transmission spectra of the graphene-based Fibonacci superlattice
(2013) Korol, Anatoliy; Isai, Valeriy
We consider the gapped graphene superlattice (SL) constructed in accordance with the Fibonacci rule. We propose to create the quasi-periodic modulation due to the difference in the values of the energy gap in different SL elements. Розглядається щільова графенова надгратка (НГ), побудована у відповідності до закону Фібоначчі. Запропоновано створювати квазіперіодичну модуляцію завдяки різниці в значеннях забороненої зони в різних елементах НГ.
Transmittivity of a disordered superlattice with impurities in the potential barriers
(1997) Korol, Anatoliy
The electron transmission rates across a disordered superlattice (SL) with impurities in the potential is evaluated. Розраховується коефіцієнт трансмісії електронів через невпорядковону надгратку з домішками в потенціальних бар’єрах.
Transmittivity of a disordered superlattice with the scatterers inside barriers in the external electric field
(1995) Korol, Anatoliy
In this work the tunneling spectra of a disordered semiconductor superlattice (SL) in the presence of external electric field are evaluated.
Tunneling conductance of the s – wave and d- wave pairing superconductive graphene – normal graphene junction
(2019) Korol, Anatoliy
Within the framework of the Blonder – Tinkham-Klapwijk formalism we calculate and analyze the conductance of the normal graphene – s-wave and independently d-wave pairing superconductive graphene junction. The eigenfunctions, the Andreev and the normal reflection rates are obtained by solving the Dirac – Bogoliubov – de Gennes equations. We consider the options of gapless and gapped graphene for both cases: – s-wave and independently d-wave.
Volt-ampere characteristic of the superconductive nanostructure with the Andreev reflection induced by the Majorana fermions
(2021) Korol, Anatoliy; Medved, Nataliya
One of the modern quantum mechanical nanostructures in which the appearance and detection of Majorana fermions takes place was considered. There are a lot of propositions onhow to create and to detect the Majorana modes. Some various structures were investigated for this purpose. The two-terminal device where a superconducting island was deposited on a three dimensional topological insulator was investigated. The branch of chiral Majorana particles was located at the interface between the semiconductor and the ferromagnetic material. In this structure, it was possible to realize the Andreev reflection induced by the Majorana fermions. To control the Majorana modes one must be able only not to create them but also to tune the resulting current-voltage characteristic of the given structure. One of the simplest models which allowed to analyz the relevant characteristics and propose the additional possibilities to tune the superconducting current was considered. In this model, an incident from the lead electron was converted into a backscattered hole with probability equal to one. Such a process may be called as a Majorana particle induced Andreev reflection. On the basis of the simplified Hamiltonian, the expressions for the transmission coefficient and the volt-ampere dependence of this structure were calculated and analyzed. It is shown that these characteristics can be flexibly adjusted using certain structure parameters, in particular, by changing the Fermi velocity of quasielectrons. Two Majorana bound states may encode a single qubit nonlocally. Such a qubit can be robust against the local source of decoherence and hence can provide a good building block for topological quantum computations. Since Majorana particles are non-Abelion fermions they may be useful in the potential applications for quantum computations free from decoherence.