On the relation between plasma rotation induced by low-frequency resonant magnetic perturbations and transport in ergodic magnetic fields

The penetration of low-frequency resonant magnetic perturbations into a tokamak plasma and their influence on the plasma rotation are analyzed in linear and quaslisinear kinetic approaches. There are two explanations of experimentally observed acceleration of plasma rotation in the direction of the plasma current. First, it is a result of the resonant absorption of the momentum of the perturbation field by the plasma. Second, it is a result of a change in the radial electric field due to the ergodization of the magnetic field and the corresponding increase in the radial electron transport. It is shown that there is no contradiction between these two explanations. These are just two different interpretations of the same phenomenon. Published in Russian in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 6, pp. 420–423. The article was translated by the authors.     

Magnetorotational instability in a nonuniform magnetic field

It is shown that the characteristics of the magnetorotational instability noticeably change in the presence of the inhomogeneity of a magnetic field in which rotation occurs. A decrease in the magnetic field with an increase in the distance from the rotation center, which is typical for astrophysical objects, can lead to a significant decrease in the threshold velocity of the object medium rotation, as well as to mitigation of the requirements on a rotation velocity profile that are necessary for the development of instability. Other examples that demonstrate the indicated effects are given.     

On twinning in smectic crystals

It is shown that mechanical twinning in smectic crystals is possible. The structure of the boundary of twins for a small disorientation of crystallites is determined. The periodic twin structure, which should appear at the tension of the smectic layer, is proposed. Original Russian Text ? V.I. Marchenko, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, p. 841.     

Stimulated radiation pressure acting on an atom nonadiabatically interacting with the field of counterpropagating frequency-modulated waves

The stimulated radiation pressure acting on an atom nonadiabatically interacting with the field of counterpropagating frequency-modulated waves is shown to reach high values typical for the rapid adiabatic passage of the instantaneous frequency of the field of the counterpropagating waves through resonance with an atomic transition. Under the appropriate choice of interaction parameters, the radiation pressure changes insignificantly in a wide range of atomic velocities. Original Russian Text ? V.I. Romanenko, L.P. Yatsenko, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 12, pp. 868–872.     

Absolute negative resistance in a nonequilibrium two-dimensional electron system in a strong magnetic field

The effect of microwave electromagnetic radiation on the resistance of the 2D electron gas in a GaAs/AlAs heterostructure in a strong magnetic field is investigated. It is shown that, under the nonequilibrium conditions caused by microwave radiation, the aforementioned 2D system exhibits giant oscillations of its resistance with varying magnetic field. When the measuring current density is small, an increase in the microwave power leads to the appearance of an absolute negative resistance at the main minimum of these oscillations, which lies near the cyclotron resonance. The experimental data are found to be in qualitative agreement with the theory of multiphoton photoinduced impurity scattering [J. Inarrea and G. Platero, Appl. Phys. Lett. 89, 052109 (2006)]. Original Russian Text ? A.A. Bykov, D.R. Islamov, D.V. Nomokonov, A.K. Bakarov, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 695–698.     

Effect of high pressure and chemical substitution on the crystal structure and magnetic state of R2Fe17 ? x Six (R = Lu or Y; x = 0 or 1.7)

The effect of high pressure on the crystal structure of the intermetallic compounds R₂Fe_{17 − x} Si_x (R = Lu or Y; x = 0 or 1.7) was studied using neutron diffraction. A correlation between changes in structural parameters and magnetic properties under the action of high pressure, as well as under chemical substitution of Si for Fe atoms, was analyzed in terms of localized moment and spin fluctuation models. The spin fluctuation model was found to describe more adequately the experimentally observed increase in the Curie temperature upon chemical substitution and the decrease in this temperature under the action of high pressure. Possible reasons for the suppression of a collinear ferromagnetic state and the occurrence of a noncollinear antiferromagnetic state in R₂Fe_17−x Si_x under pressure are discussed based on estimated differences between the total energy minima of these states. Original Russian Text ? D.P. Kozlenko, V.I. Voronin, V.P. Glazkov, B.N. Savenko, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 675–680.     

On the source of auroral kilometric radiation

The radiation pattern has been determined on the basis of the comparative analysis of auroral kilometric radiation (AKR) received in the space-diversity mode by two satellites, Interball-2 and Polar. The radiation propagates in a cone with an opening angle ∼±25° and the axis aligned with the local magnetic field. The results con-firm the theoretical estimates that the source boundaries play a significant role in the generation of the auroral kilometric radiation and in the formation of the radiation pattern. Original Russian Text ? M.M. Mogilevsky, T.V. Romantsova, J. Hanasz, T.M. Burinskaya, R. Schreiber, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 819–821.     

Formation of nanosystems under near-equilibrium copper condensation in an ultrapure inert medium

Mechanisms of the self-organization of nanosystems at the condensation of the extremely weak steady flows of copper vapors obtained in magnetron sputtering in an ultrapure argon are studied. It is shown that the free-energy minimization near equilibrium condensation creates prerequisites for the self-organization of statistically homogeneous layers of nanoclusters and determines the transition to the formation of nanosystems in the form of fractal networks. Original Russian Text ? V.I. Perekrestov, A.S. Kornyushchenko, Yu.A. Kosminskaya, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 12, pp. 879–883.     

Anomalous hall effect in HoB12

Within a wide temperature range of 1.8–300 K, the Hall effect in holmium dodecaboride is investigated. The measurements of the angular dependences of the Hall resistance ρ_H(φ, T, H) for HoB₁₂ performed in a high magnetic field up to 80 kOe at helium and intermediate temperatures made it possible to separate the normal and anomalous contributions to the Hall effect. Analysis of the anomalous component behavior in the paramagnetic and Néel phases suggests the appearance of the 5d-state magnetic polarization (the spin polaron effect) and makes it possible to compare the revealed features of the Hall coefficient R _H(T, H) with the H-T magnetic phase diagram of HoB₁₂. Original Russian Text ? N.E. Sluchanko, D.N. Sluchanko, V.V. Glushkov, S.V. Demishev, N.A. Samarin, N.Yu. Shitsevalova, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 691–694.     

Magnetic breakdown and quantum magnetotransport with a constant pseudospin under tilted magnetic fields in an n -In x Ga1? x As/GaAs double quantum well

A procedure is proposed for precise scanning of the (B _⊥, B _‖) plane between the magnetic field projections that are perpendicular and parallel to (quasi-)two-dimensional layers when measuring their longitudinal and Hall magnetoresistances. Investigations of a n-In _x Ga_1−x As/GaAs double quantum well (x ≈ 0.2) performed using this procedure make it possible to reveal a number of the features of the magnetoresistance, which appear due to a complex energy spectrum of the double quantum well in a parallel field, and to separate them from the structures associated with the magnetic breakdown. The trajectories representing the features of the magnetoresistance in the (B _⊥, B _‖) plane are described by the semiclassical calculations of the quantization of the energy spectrum of the double quantum well under the action of the perpendicular field component. The structures appearing due to the magnetic breakdown are amplified with increasing the total magnetic field magnitude and, in the samples with low mobility, completely suppress the features caused by the motion of an electron with a constant pseudospin component. The peaks corresponding to the magnetic breakdown are split in a strong parallel field due to the spin splitting of the Landau levels. These splittings correspond to the effective Landé factor |g*| ≈ 3. Original Russian Text ? M.V. Yakunin, S.M. Podgornykh, V.N. Neverov, 2007, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 132, No. 1, pp. 241–249.     

High-frequency acoustic noise of Lake Baikal

High-frequency noise of Lake Baikal is investigated using a submersible self-contained instrument to determine the noise background for the acoustic detection of superhigh-energy neutrinos. It is found that, under stationary and uniform meteorological conditions, the integral noise power in the frequency band 1–50 kHz is virtually independent of depth and is 10–200 mPa or more, depending on the specific conditions. The noise itself contains multiple short pulses of different amplitudes and shapes. Original Russian Text ? V.M. Aĭnutdinov, V.A. Balkanov, I.A. Belolaptikov, L.B. Bezrukov, N.M. Budnev, R.V. Vasil’ev, R. Wischnewski, O.N. Gaponenko, R.Yu. Gnatovskiĭ, O.A. Gress, T.I. Gress, O.G. Grishin, I.A. Danil’chenko, Zh.-A.M. Dzhilkibaev, A.A. Doroshenko, A.N. Dyachok, G.V. Domogatskiĭ, V.A. Zhukov, A.M. Klabukov, A.I. Klimov, S.I. Klimushin, K.V. Konishchev, A.A. Kochanov, A.P. Koshechkin, V.F. Kulepov, L.A. Kuz’michev, B.K. Lubsandorzhiev, T. Mikolajskiĭ, M.B. Milenin, R.R. Mirgazov, S.P. Mikheev, é.A. Osipova, A.I. Panfilov, A.A. Pavlov, G.L. Pan’kov, L.V. Pan’kov, E.N. Pliskovskiĭ, V.A. Poleshchuk, E.G. Popova, P.G. Pokhil, V.V. Prosin, M.I. Rozanov, V.Yu. Rubtsov, B.A. Tarashchanskiĭ, S.V. Fialkovskiĭ, A.G. Chenskiĭ, B.A. Shaĭbonov, Ch. Spiering, O. Streicher, I.V. Yashin, 2006, published in Akusticheskiĭ Zhurnal, 2006, Vol. 52, No. 5, pp. 581–591.     

Measurement of the e+e? → π+π? cross section with the CMD-2 detector in the 370–520-MeV energy range

The results of the experiment on the measurement of the e ⁺ e ⁻ → π⁺π⁻ cross section in a cm energy range of 370–520 MeV are presented. The systematic measurement error is equal to 0.7%. In the vector dominance model, the pion electromagnetic radius is calculated using all the CMD-2 data on the pion form factor. The cross section for the production of a muon pair is measured in the energy range of the experiment. Original Russian Text ? V.M. Aul’chenko, R.R. Akhmetshin, V.Sh. Banzarov, L.M. Barkov, N.S. Bashtovoĭ, D.V. Bondarev, A.E. Bondar’, A.V. Bragin, N.I. Gabyshev, D.A. Gorbachev, A.A. Grebenyuk, D.N. Grigor’ev, S.K. Dhawan, D.A. Epifanov, A.S. Zaĭtsev, S.G. Zverev, F.V. Ignatov, V.F. Kazanin, S.V. Karpov, I.A. Koop, P.P. Krokovny, A.S. Kuz’min, I.B. Logashenko, P.A. Lukin, A.P. Lysenko, A.I. Mil’shteĭn, K.Yu. Mikhaĭlov, I.N. Nesterenko, M.A. Nikulin, A.V. Otboev, V.S. Okhapkin, E.A. Perevedentsev, A.S. Popov, S.I. Redin, B.L. Roberts, N.I. Root, A.A. Ruban, N.M. Ryskulov, A.L. Sibidanov, V.A. Sidorov, A.N. Skrinsky, V.P. Smakhtin, I.G. Snopkov, E.P. Solodov, J.A. Thompson, G.V. Fedotovich, B.I. Khazin, V.W. Hughes, A.G. Shamov, Yu.M. Shatunov, B.A. Shvarts, S.I. éĭdel’man, Yu.V. Yudin, 2006, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2006, Vol. 84, No. 8, pp. 491–495.     

Effect of the size of nanoparticles on the properties of a capacitive high-frequency discharge

The properties of a capacitive HF discharge with growing nanoparticles are studied with the use of kinetic PIC-MCC simulation. At the initial stage of growth, the nanoparticles are shown to be localized at the interface between the near-electrode layer and quasi-neutral plasma, where the rate of ionization by electron impact has the maximum value. At the beginning of formation of particles, plasma parameters change rapidly and a transition between the capacitive and spatial discharge burning modes is observed for a certain critical size of the particles. If the growth of the dust particles continues, their distribution over the discharge becomes more uniform and the steady-state parameters of the gas-discharge plasma hardly change. Original Russian Text ? I.V. Shveigert, F.M. Peeters, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 657–661.     

Proton and light-ion acceleration to relativistic GeV energies by the superstrong laser radiation interacting with a structured plasma target

A new scheme is proposed for proton and light-ion acceleration to relativistic energies by superstrong laser radiation interacting with a structured plasma target. The proposal consists in the use of two-component targets consisting of heavy and light ions, where an ambipolar field is formed under the action of the ponderomotive force of incident radiation, and, in contrast to the traditional schemes, acceleration starts from the front boundary of the layer. It is shown that, for the optimized target parameters, monoenergetic GeV ion beams can be produced for radiation pulse intensities on the order of 10²¹−10²² W/cm². Original Russian Text ? A.V. Korzhimanov, A.A. Gonoskov, A.V. Kim, A.M. Sergeev, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 662–669.     

Optical study of the electronic structure and magnetic ordering in a weak ferromagnet FeBO3

Spectral dependences of the relative permittivity ɛ = ɛ₁ − iɛ₂ of a uniaxial weak ferromagnet FeBO₃ are measured for two principal polarizations in the energy range 0.6–5.6 eV. The positions have been determined for the charge-transfer transitions that make the main contribution to absorption above the bandgap and determine the refractive-index dispersion below the bandgap. The isotropic magnetic contribution to the refractive index has been detected by studying the temperature dependence of the refractive index in the range 100–700 K; its value (≈2 × 10⁻²) is found to be record high for magnetic dielectrics. The energy shift of the effective oscillator, which characterizes the shift of the positions of the charge-transfer transitions due to magnetic ordering, is determined from these data within the framework of a single-oscillator model. The value of the exchange striction in FeBO₃ is determined from optical measurements. Original Russian Text ? P.A. Markovin, A.M. Kalashnikova, R.V. Pisarev, Th. Rasing, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 822–827.     

Alternative method of the opening of cavities in small icosahedral electrolytic-metal particles

Results of an experiment on the opening of cavities in small icosahedral electrolytic-copper particles by means of an experimental technique alternative to the chemical etching of their surface are presented. This experimental technique is theoretically justified. Original Russian Text ? I.S. Yasnikov, A.A. Vikarchuk, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 699–701.     

Conductance of short quantum wires with sharp boundaries

The conductance of short ballistic wires with boundaries, whose curvature radius is comparable to the electron wavelength, is investigated. It is found that, in such wires, no conductance quantization takes place. Instead, pronounced interference effects are observed. These effects are related to the Fabry-Perot interference by the wire edges and with the mesoscopic interference caused by the coherent scattering of electrons by the wire edges and by the impurities located in the near-wire regions of the 2D electron gas. Original Russian Text ? D.A. Kozlov, Z.D. Kvon, A.E. Plotnikov, D.V. Shcheglov, A.V. Latyshev, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 10, pp. 752–756.     

On the possibility of the nondegenerate parametric amplification of optical waves at low-frequency pumping

It is shown that parametric amplification at low-frequency pumping can be implemented in coupled nonlinear optical interactions in aperiodic nonlinear photonic crystals created by the method of the superposition of the modulation of the second-order susceptibility. In this process, the intensities of waves with frequencies higher than the pump frequency increase monotonically with the interaction length as in the case of the traditional process of parametric amplification at high-frequency pumping. The dependence of the gain factor on the coupling constants of interacting waves is obtained. The process under consideration makes it possible to ensure the tuning of the generated frequency in the ultraviolet range upon pumping in the visible range. Analysis of the process is performed on the example of aperiodic nonlinear photonic crystals of lithium niobate. Original Russian Text ? A.S. Chirkin, I.V. Shutov, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 803–807.     

Polarization transformations of multimode light fields

The concept of P-quasispin is used as a framework for developing a formalism for polarization transformation by means of lossless polarization-changing optical elements for both classical and quantum multimode light fields. As an example, a classification of transformations of this kind is presented for two-mode biphoton fields that implement the information-theoretic concepts of qutrit and ququart (quantum systems in three-and four-dimensional Hilbert states, respectively). Original Russian Text ? V.P. Karassiov, S.P. Kulik, 2007, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 131, No. 1, pp. 37–53.