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Search Results: 1 - 10 of 539348 matches for " V. A. Volkov "
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V. A. Kochetkov,V. V. Volkov
Scientific Herald of the Voronezh State University of Architecture and Civil Engineering , 2011,
Abstract: Problem statement. There is a problem of determining the state airfield and road foundations by non-destructive methods. This problem is due to the inability to detect changes in the road base structure during its operation. The destructive processes reduce the load-bearing ability of the foundation, which can lead to the structure destruction; especially it is the case with multi-cycle load close to the limit load.Results. Structure examination technique based on dipole element introduction into the foundation material, and experimental setup sensitive to change in density of their distribution in the array caused by change in structure were developed.Conclusions. Developed technique allows one to detect the processes resulting in base structure changes and as a consequence in the emergence of defects affecting the safety of runway opera-tions, at the early stages of transport structure operation.
Quantum confinement, energy spectra and backscattering of Dirac fermions in quantum wire in magnetic field
V. V. Enaldiev,V. A. Volkov
Physics , 2013,
Abstract: We address the problems of an energy spectrum and backscattering of massive Dirac fermions confined in a cylindrical quantum wire. The Dirac fermions are described by the 3D Dirac equation supplemented by time-reversal-invariant boundary conditions at a surface of the wire. Even in zero magnetic field, spectra quantum-confined and surface states substantially depend on a boundary parameter a0. At the wire surface with a0 > 0 (a0 < 0) the surface states form 1D massive subbands inside (outside) the bulk gap. The longitudinal magnetic field transforms the energy spectra. In the limit of the thick wires and the weak magnetic fields, the 1D massless surface subbands arise at half- integer number of magnetic flux quanta passing through the wire cross section. We reveal conditions when backscattering of the surface Dirac fermions by a non-magnetic impurity is suppressed. In addition, we calculate a conductance formed by the massless surface Dirac fermions in the magnetic field in collisional and ballistic regimes.
Surface States of 3D Dirac Fermions in Cylindrical Nanowire
V. V. Enaldiev,V. A. Volkov
Physics , 2015,
Abstract: We derive a theory for 3D Dirac fermions confined in a cylindrical nanowire. The system is described by the isotropic Dirac equation supplemented by time-reversal-invariant boundary condition at surface of the nanowire. In this approach properties of surface structure of the nanowire is described by a single phenomenological real parameter $a_0$. The sign of $a_0$ qualitatively distinguishes spectra of the surface states. At $a_0>0$ ($a_0<0$) the surface states form 1D massive subbands with hyperbolic dispersion inside (outside) the bulk gap. In longitudinal magnetic field the surface states lead to the Aharonov-Bohm oscillations (with Berry phase $\pi$) of electrical conductivity of the nanowire. Two gapless surface subbands arise periodically in energy spectra at $a_0\geq 0$. In case of the nanowire with smooth inhomogeneous cross section, 1D supersymmetric-like state controlled by magnetic field may emerge.
Long-range thermoelectric effects in mesoscopic superconductor-normal metal structures
A. F. Volkov,V. V. Pavlovskii
Physics , 2005, DOI: 10.1103/PhysRevB.72.014529
Abstract: We consider a mesoscopic four-terminal superconductor/normal metal (S/N) structure in the presence of a temperature gradient along the N wire. A thermoemf arises in this system even in the absence of the thermoelectric quasiparticle current if the phase difference between the superconductors is not zero. We show that the thermoemf is not small in the case of a negligible Josephson coupling between two superconductors. It is also shown that the thermoelectric voltage has two maxima: one at a low temperature and another at a temperature close to the critical temperature. The obtained temperature dependence of the thermoemf describes qualitatively experimental data.
Method of quasiclassical Green's functions in the theory of transport phenomena in superconducting mesoscopic structures
A. F. Volkov,V. V. Pavlovskii
Physics , 1997, DOI: 10.1063/1.55281
Abstract: A short introduction to the theory of matrix quasiclassical Green's functions is given and possible applications of this theory to transport properties of mesoscopic superconducting-normal metal (S/N) structures are considered. We discuss a simplified version of these equations in the diffusive regime and in the case of a weak proximity effect. These equations are used for the calculation of the conductance of different S/N structures. Long-range, phase-coherent effects are studied in a 4-terminal S/N/S structures under conditions when the Josephson critical current is negligible. It is shown that the Josephson effects may be observed in this system if an additional current flows through the N electrode.
Residual Resistance in a 2DES: A Phenomenological Approach
A. F. Volkov,V. V. Pavlovskii
Physics , 2003,
Abstract: We consider a simple phenomenological model of a semiconductor with absolute negative conductance in a magnetic field. We find the form of the domains of the electric field and current which arise as a result of an instability of a uniform state. We show that in both Corbino disc and Hall bar samples the residual conductance and resistance are negative and exponentially small; they decrease exponentially with increasing length L_{x,y}.
Study of narrow baryon resonance decaying into $K^0_s p$ in $pA$-interactions at $70 GeV/c$ with SVD-2
A. Kubarovsky,V. Popov,V. Volkov
Statistics , 2006,
Abstract: The inclusive reaction $p A \to pK^0_s + X$ was studied at IHEP accelerator with $70 GeV$ proton beam using SVD-2 detector. Two different samples of $K^0_s$, statistically independent and belonging to different phase space regions were used in the analyses and a narrow baryon resonance with the mass $M=1523\pm 2(stat.)\pm 3(syst.) MeV/c^2$ was observed in both samples of the data
Bernstein modes and giant microwave response of two-dimensional electron system
V. A. Volkov,A. A. Zabolotnykh
Physics , 2013, DOI: 10.1103/PhysRevB.89.121410
Abstract: We report on a new contribution to the microwave response of a two-dimensional electron system in magnetic field which originates from excitation of virtual Bernstein modes. These collective modes emerge as a result of interaction between usual magnetoplasmon mode and cyclotron resonance harmonics. The electrons are found to experience a strongly enhanced radiation field when its frequency falls in a gap of the Bernstein modes spectrum. This field can give rise to nonlinear effects, one of which, the parametric cyclotron resonance, is discussed. We argue that this resonance leads to a plasma instability in the ultraclean system. The instability-induced heating is responsible for the giant photoresistivity spike recently observed in the vicinity of the 2nd cyclotron resonance harmonic.
Dynamics of Fluxon Lattice in Two Coupled Josephson Junctions
A. F. Volkov,V. A. Glen
Physics , 1998, DOI: 10.1088/0953-8984/10/33/001
Abstract: We study theoretically the dynamics of a fluxon Lattice (FL) in two coupled Josephson junctions. We show that when the velocity of the moving FL exceeds certain values $(V_{a,b})$, sharp resonances arise in the system which are related to the excitation of the optical and acoustic collective modes. In the interval $(V_a, V_b)$ a reconstruction of the FL occurs. We also establish that one can excite localized nonlinear distortions (dislocations) which may propagate through the FL and carry an arbitrary magnetic flux.
Spin splitting of two dimensional states in the conduction band of asymmetric heterostructures: contribution from the atomically sharp interface
Zh. A. Devizorova,V. A. Volkov
Physics , 2014, DOI: 10.1134/S002136401315006X
Abstract: The effect of an atomically sharp impenetrable interface on the spin splitting of the spectrum of two-dimensional electrons in heterostructures based on (001) III-V compounds has been analyzed. To this end, the single band Hamiltonian $\Gamma_{6c}$ for envelope functions is supplemented by a general boundary condition taking into account the possibility of the existence of Tamm states. This boundary condition also takes into account the spin-orbit interaction, the asymmetry of a quantum well, and the lack of inversion symmetry in the crystal and contains the single phenomenological length $R$ characterizing the structure of the interface at atomic scales. The model of a quasitriangular well created by the electric field $F$ has been considered. After the unitary transformation to zero boundary conditions, in the modified Hamiltonian interfacial contribution appears, from which the two-dimensional spin Hamiltonian is obtained through averaging over the fast motion along the normal. In the absence of magnetic field $\boldsymbol B$, this contribution is the sum of the Dresselhaus and the Bychkov-Rashba terms with the constants renormalized owing to the interfacial contribution. In the field $\boldsymbol B$ containing the quantizing component $B_z$, the off - diagonal (in cubic axes) components of the $g$-factor tensor are linear functions of $|B_z|$ and the number of the Landau level $N$. The results are in qualitative agreement with the experimental data.
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