Kharkov, Ukraine

The National Technical University "Kharkiv Polytechnic Institute" ), in the city of Kharkiv, is the largest and oldest technical university in eastern Ukraine. Founded in 1885, it is the second-oldest technical university in the Russian Empire and in the territory of modern Ukraine . Wikipedia.


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Gomonay H.V.,Kharkiv Polytechnic Institute | Loktev V.M.,NASU Bogolyubov Institute for Theoretical Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Recent experiments show that spin-polarized current may influence the state of generally accessory element of spin valves, an antiferromagnetic (AFM) layer, which is used for "pinning." Here we study the dynamics of AFM component of the "pinned" ferromagnetic (FM) layer induced by simultaneous application of the spin-polarized current and external magnetic field. We find stability range of such a configuration of FM/AFM system in which orientation of FM magnetization is parallel to AFM vector. We calculate the field dependence of the critical current for different orientations of the external magnetic field with respect to the crystal axes of FM/AFM bilayer. We show the possibility of stable current-induced precession of AFM vector around FM magnetization with the frequency that linearly depends on the bias current. Furthermore, we estimate an optimal duration of the current pulse required for switching between different states of FM/AFM system and calculate the current and field dependencies of switching time. The results obtained reveal the difference between dynamics of ferromagnets and antiferromagnets subjected to spin transfer torques. © 2010 The American Physical Society.


Moskalets M.,Kharkiv Polytechnic Institute
Physical Review Letters | Year: 2014

I present the Floquet scattering matrix theory of low-frequency heat fluctuations in driven quantum-coherent conductors in the linear response regime and beyond. The Floquet theory elucidates the use of the Callen-Welton fluctuation-dissipation theorem for a description of heat fluctuations in a multiterminal case. The intrinsic fluctuations of energy of dynamically excited electrons are identified as the fundamental source of heat noise not revealed by the electrical noise. The role of backscattering in the increase of heat noise above the level defined by the Callen-Welton theorem is highlighted. The exception is the case when a conductor is driven by a Lorentzian voltage pulse with quantized flux. The heat noise in this case falls down to the level pertaining to a linear response regime. © 2014 American Physical Society.


Gomonay O.,Kharkiv Polytechnic Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

Antiferromagnets (AFMs), in contrast to ferromagnets, show a nontrivial magnetic structure with zero net magnetization. However, they share a number of spintronic effects with ferromagnets, including spin pumping and spin-transfer torques. Both phenomena stem from the coupled dynamics of free carriers and localized magnetic moments. In the present paper I study the adiabatic dynamics of spin-polarized electrons in a metallic AFM exhibiting a noncollinear 120° magnetic structure. I show that the slowly varying AFM spin texture produces a non-Abelian gauge potential related to the time and space gradients of the Néel vectors. Corresponding emergent electric and magnetic fields induce rotation of spin and influence the orbital dynamics of free electrons. I discuss both the possibility of a topological spin Hall effect in the vicinity of topological AFM solitons with nonzero curvature and rotation of the electron spin traveling through the AFM domain wall. © 2015 American Physical Society.


Moskalets M.,Kharkiv Polytechnic Institute
Physical Review Letters | Year: 2016

A voltage pulse of a Lorentzian shape carrying half of the flux quantum excites out of a zero-temperature Fermi sea an electron in a mixed state, which looks like a quasiparticle with an effectively fractional charge e/2. A prominent feature of such an excitation is a narrow peak in the energy distribution function lying exactly at the Fermi energy μ. Another spectacular feature is that the distribution function has symmetric tails around μ, which results in a zero-energy excitation. This sounds improbable since at zero temperature all available states below μ are fully occupied. The resolution lies in the fact that such a voltage pulse also excites electron-hole pairs, which free some space below μ and thus allow a zero-energy quasiparticle to exist. I discuss also how to address separately electron-hole pairs and a fractionally charged zero-energy excitation in an experiment. © 2016 American Physical Society.


Kabanov A.A.,Kharkiv Polytechnic Institute
WSEAS Transactions on Systems and Control | Year: 2014

This paper is devoted to the development of an optimal control system of trajectory movement of a mobile robot. Synthesis of the trajectory control law is based on the methods of optimal control and asymptotical methods of singular perturbation theory. Singular perturbation theory's methods are used for reducing the order of the solving problem and it helps to simplify the realization of the control law. Proposed system has two control loops: position control loop and velocity control loop. Based on this, the structure of the control system is represented by two modules: the reference and the executive. In this work the results of experimental verification of the trajectory control system at the mobile robot Rover5 with the tank-type chassis are presented.


Moskalets M.,Kharkiv Polytechnic Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

A new principle of manipulation of an electron phase is proposed. The phase is added not directly to an electron but to a finite-length portion of the Fermi sea associated with it, which I name a phase carrier. This phase can be read out with the help of an imbalanced interferometer, where the phase carrier interferes with the reference Fermi sea. As a result of such interference, the same value but opposite sign charge appears at the interferometer's outputs. A phase carrier can be created, for instance, with the help of an on-demand single-electron source able to produce excitations with multiple-peak density profiles. © 2014 American Physical Society.


Moskalets M.,Kharkiv Polytechnic Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

Two single-particle sources coupled in series to a chiral electronic waveguide can serve as a probabilistic source of two-particle excitations with tunable properties. The second-order correlation function, characterizing the state of emitted electrons in space-time, is expressed in terms of the Floquet scattering matrix of a source. It is shown that the Fourier transform of the correlation function, characterizing the emitted state in energy space, can be accessed with the help of an energy resolved shot-noise measurement. The two-electron state emitted adiabatically is discussed in detail. In particular, the two-electron wave function is represented via two different sets of single-particle wave functions accessible experimentally. © 2014 American Physical Society.


Zubarev E.N.,Kharkiv Polytechnic Institute
Physics-Uspekhi | Year: 2011

Reactive diffusion in nanomaterials differs widely from that in bulk materials. Reviewed in this paper are the basic models and experimental data on how diffusion and phase transformations occur in multilayer nanosystems as these are being prepared and subsequently thermally annealed. The growth kinetics of amorphous silicide phases in Sc/Si and Mo/Si multilayer periodic systems are studied using the combination of high-resolution transmission electron microscopy and small-angle X-ray diffraction. A model is proposed for silicon diffusion through amorphous silicide that undergoes structural relaxation and crystallization as it grows. Anisotropic diffusion and growth of the silicide phase at adjacent interfaces are studied, and the diffusion parameters are measured for the earliest stages of diffusion annealing. © 2011 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.


Moskalets M.,Kharkiv Polytechnic Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

I analyze the correlation function of currents generated by a periodically driven quantum capacitor emitting single electrons and holes into a chiral waveguide. I compare adiabatic and nonadiabatic transient working regimes of a single-electron emitter and find a striking difference between the correlation functions in the two regimes. Quite generally, for a system driven with frequency Ω the correlation function depends on two frequencies ω and ℓΩ-ω, where ℓ is an integer. For an emitter driven nonadiabatically the correlation functions for different ℓ are similar and almost symmetric in ω, while in the case of adiabatic driving the correlation functions for ℓ≠0 are highly asymmetric in ω and exceed significantly the one corresponding to ℓ=0. Under optimal operating conditions the correlation function for odd ℓ is zero. © 2013 American Physical Society.


Fedorov V.A.,Kharkiv Polytechnic Institute
Composites Part B: Engineering | Year: 2014

Unidirectional fibre-reinforced composites with symmetrical structure, loaded by transverse shear, are investigated. The focus of the paper is on mathematical models for different representative cells. Transverse shear of symmetrical composites, unlike other types of loads, does not allow application of Curie's principle for detection of possible symmetry of mechanical fields. The existence of such symmetry is shown by employing the theorem proven earlier by the author. Respective boundary value problems can be formulated for the minimal representative cell. In contrast to the existing approach, which contains inaccuracy of Saint-Venant's principle, the proposed formulations are exact. It is shown that employing the symmetry cell in numerical solutions can reduce computational cost by 2-3 orders. With the use of Lagrange's and Castigliano's variational principles in generalised form, it is proven that solutions for the "infinite" cell give lower and upper bounds for the transverse shear modulus. It is proven, as well, that these bounds lie within the Voigt and Reuss bounds. © 2013 Elsevier Ltd. All rights reserved.

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