共查询到20条相似文献,搜索用时 78 毫秒
1.
V. A. Burdov 《JETP Letters》1999,70(6):390-395
It is shown that when a strong ac electric field acts on an electron in a double quantum well, the dipole moment is an almost
periodic function of the dc voltage applied to the structure. An antipolarization effect — the structure is polarized in a
direction opposite to the external field — appears during one half of the period.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 6, 386–391 (25 September 1999) 相似文献
2.
D. E. Feldman 《JETP Letters》1999,70(2):135-140
The random field and random anisotropy N-vector models are studied with the functional renormalization group in 4−ε dimensions. The random anisotropy Heisenberg (N=3) model has a phase with an infinite correlation length at low temperatures and weak disorder. The correlation function
of the magnetization obeys a power law 〈m(r
1)m(r
2)〉∼|r
1−r
2|− 0.62ε. The magnetic susceptibility diverges at low fields as χ∼H
−1+0.15ε. In the random field N-vector model the correlation length is finite at arbitrarily weak disorder for any N>3.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 130–135 (25 July 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
3.
N. S. Ginzburg I. V. Zotova I. V. Konoplev A. S. Sergeev V. G. Shpak S. A. Shunailov M. R. Ul’maskulov M. I. Yalandin 《JETP Letters》1996,63(5):331-335
Intense (several hundreds of kilowatts) subnanosecond coherent microwave radiation — cyclotron superradiance of an electron
swarm moving in a uniform magnetic field — was recorded. The maximum power of the radiation was observed under group synchronization
conditions, when the translational velocity of the swarm is equal to the group velocity of the waves in the waveguide channel.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 322–325 (10 March 1996) 相似文献
4.
A. A. Gorbatsevich Yu. V. Kopaev I. V. Kucherenko O. E. Omel’yanovskii V. I. Tsebro V. V. Kapaev 《JETP Letters》1998,68(5):404-411
A new phenomenon is observed experimentally in a heavily doped asymmetric quantum-size structure in a magnetic field parallel
to the quantum-well layers — a transverse magnetoresistance which is asymmetric in the field (there can even be a channge
in sign) and is observed in the case that the structure has a built-in lateral electric field. A model of the effect is proposed.
The observed asymmetry of the magnetoresistance is attributed to an additional current contribution that arises under nonequilibrium
conditions and that is linear in the gradient of the electrochemical potential and proportional to the parameter characterizing
the asymmetry of the spectrum with respect to the quasimomentum.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 380–385 (10 September 1998) 相似文献
5.
F. N. Ibrahim 《Il Nuovo Cimento D》1995,17(10):1089-1101
Summary Analytical and numerical solutions for the momentum and thermal boundary layer equations of a non-Newtonian power law fluid
are presented. The flow is assumed to be under the influence of an external magnetic fieldB (x) applied perpendicular to the surface and an electric fieldE(x) perpendicular toB(x) and the direction of the longitudinal velocity in the boundary layer. For the power law fluid it is assumed that the shear
stress is proportional to then-th power of the velocity gradient andn is called the flow index. The variations of the velocity fieldf′, the temperature field θ, the shear stress on the surfaceτ
W
, the displacement thicknessδ
1 and the momentum thicknessδ
2 with the magnetic-field parameter γ, the flow indexn, the heat transfer indexS and the Prandtl number Pr are studied. It is found that, if the outer flow velocityU(x) (potential flow) is proportional to the arc lengthx raised to a powerm, then the similarity solution for the thermal boundary layer equation is possible only whenm=1/3, which represents flow past a wedge of included angle π/2. It is established that the temperature of the wedge increases
with the increase of γ, Pr,S and the decrease ofn. In general the magnetic field can be used as a heater for the surface of the wedge. 相似文献
6.
A contribution to electromagnetic power losses, additional to the losses due to eddy currents and exhibiting a resonance frequency
dependence with the main maximum near 1 GHz, has been observed for the ferromagnetic alloy Pd2AuFe in the frequency range 0.9 MHz–10 GHz in the absence of an external constant magnetic field. Investigations performed
in a dc magnetic field show that this effect is a natural ferromagnetic resonance due to intradomain magnetization precession
in the effective magnetic-anisotropy field.
Fiz. Tverd. Tela (St. Petersburg) 40, 1900–1904 (October 1998) 相似文献
7.
The motion of plasma electrons in a stochastic electromagnetic field is studied in the low-conductivity limit. It is shown
that under very general conditions, in the presence of a nonzero average chirality of the small-scale electromagnetic field,
the effective current depends on the curl of the applied electric field, j=§ E+§κcurl E, just as for similar dependences for the electric displacement and magnetic induction vectors in optically active and artificial
chiral media. Under certain conditions such an Ohm’s law leads to growth of the magnetic field, the structure of the growth
being dependent on the conductivity of the medium.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 268–273 (25 August 1999) 相似文献
8.
É. B. Abubakirov A. N. Denisenko N. F. Kovalev E. A. Kopelovich A. V. Savel’ev E. I. Soluyanov M. I. Fuks V. V. Yastrebov 《Technical Physics》1999,44(11):1356-1359
A new version of the relativistic backward wave oscillator (BWO) is proposed and investigated experimentally, where the cutoff
(for the working mode mode) taper at the cathode end is replaced by a selective Bragg-type mode converter. In the experimental
BWO model, which operates in the three-centimeter range and is equipped with a mode converter based on a slightly corrugated
waveguide, a radiated power of 700 MW in pulses of duration up to 100 ns with an output spatial structure similar to a Gaussian
wave beam is obtained at an accelerating potential of 0.8 MV and a focusing magnetic field of 7 kOe.
Zh. Tekh. Fiz. 69, 102–105 (November 1999) 相似文献
9.
We have investigated the proof of the H theorem within a
manifestly covariant approach by considering the relativistic
statistical theory developed in [G. Kaniadakis, Phys. Rev. E 66, 056125 (2002); G. Kaniadakis, Phys. Rev. E 72, 036108 (2005)]. As it
happens in the nonrelativistic limit, the molecular chaos hypothesis
is slightly extended within the Kaniadakis formalism. It is shown
that the collisional equilibrium states (null entropy source term)
are described by a κ power law generalization of the
exponential Juttner distribution, e.g.,
,
with θ=α(x)+βμpμ, where α(x) is a
scalar, βμ is a four-vector, and pμ is the
four-momentum. As a simple example, we calculate the relativistic
κ power law for a dilute charged gas under the action of an
electromagnetic field Fμν. All standard results are readly
recovered in the particular limit κ→0. 相似文献
10.
B. S. Dumesh M. I. Kurkin S. V. Petrov A. M. Tikhonov 《Journal of Experimental and Theoretical Physics》1999,88(6):1221-1228
The spectrum and intensities of NMR lines are investigated experimentally and theoretically for excitation by an alternating
magnetic field h‖ parallel to a static field H in the quasi-one-dimensional, six-sublattice antiferromagnet CsMnBr3. According to theory, two new NMR lines, which are not excited by a transverse magnetic field h
⊥, are observed near the phase transition from triangular to collinear structure (H=H
c
) [JETP 86, 197 (1998)].
Zh. éksp. Teor. Fiz. 115, 2228–2241 (June 1999) 相似文献
11.
V. S. Egorov E. P. Krasnoperov F. V. Lykov U. Zimmermann G. Solt C. Baines D. Herlach 《Physics of the Solid State》1998,40(3):482-484
We have observed diamagnetic domains (Condon domains) in a beryllium single crystal in magnetic fields H⩽3 T (H∥[0001]) at liquid-helium temperatures. The formation of the domain structure was determined according to magnetic-breakdown
quantum oscillations of the resistance thermoelectric power as well as according to the splitting of the resonance peak of
the free spin precession frequency of muons (μSR). The alternation of a uniform state (with one μSR peak) and a state with
domain structure (with two peaks) is consistent as regards the periodicity with the de Haas-van Alphen effect, the period
is ΔH≅78 Oe, and the range of existence of domains and the difference in their magnetizations are ΔB=4πΔM=B
2−B
1≅30 Oe.
Fiz. Tverd. Tela (St. Petersburg) 40, 524–526 (March 1998) 相似文献
12.
Spectral Analysis for Systems of Atoms and Molecules Coupled to the Quantized Radiation Field 总被引:2,自引:2,他引:0
Volker Bach Jürg Fröhlich Israel Michael Sigal 《Communications in Mathematical Physics》1999,201(2):249-290
We consider systems of static nuclei and electrons – atoms and molecules – coupled to the quantized radiation field. The interactions
between electrons and the soft modes of the quantized electromagnetic field are described by minimal coupling, p→p−e
A (x), where A(x) is the electromagnetic vector potential with an ultraviolet cutoff. If the interactions between the electrons and the quantized
radiation field are turned off, the atom or molecule is assumed to have at least one bound state. We prove that, for sufficiently
small values of the fine structure constant α, the interacting system has a ground state corresponding to the bottom of its
energy spectrum. For an atom, we prove that its excited states above the ground state turn into metastable states whose life-times
we estimate. Furthermore the energy spectrum is absolutely continuous, except, perhaps,
in a small interval above the ground state energy and around the threshold energies of the atom or molecule.
Received: 3 September 1998 / Accepted: 17 March 1999 相似文献
13.
This paper discusses the effect of magnetic translational symmetry on the vortex structure in superconducting crystals with
a large basis in artificial Josephson media (regular lattices of superconducting clusters) prepared with opal as the base
material. For external magnetic fields lower than the upper critical field, the lattice Ginzburg-Landau model reduces to the
two-dimensional Frenkel’-Kontorova model which in some cases is exactly solvable, in which the crystal lattice plays the role
of an “hard sublattice” while the deformable vortex lattice plays the role of a “soft sublattice.” It is shown that static
shear waves in the vortex lattice are solutions to the two-dimensional sine-Gordon equation with an additional condition of
incompressibility implied by flux quantization. The pinning energy is found as a function of the magnetic field, nearness
to the transition line, and the crystal lattice constant.
Fiz. Tverd. Tela (St. Petersburg) 39, 1158–1162 (July 1997) 相似文献
14.
The possibility of using a disclination approach to describe the structure and properties of fullerenes is discussed. It is
shown that the conversion of a planar carbon monolayer into a spherical macromolecule can be viewed as the result of introducing
12 disclinations with power π/3 into the original layer.
Fiz. Tverd. Tela (St. Petersburg) 40, 1178–1180 (June 1998) 相似文献
15.
F. Atrio-Barandela J. Einasto S. Gottlöber V. Müller A. Starobinsky 《JETP Letters》1997,66(6):397-403
We calculate the temperature anisotropies of the cosmic microwave background (CMB) for several initial power spectra of density
perturbations with a built-in scale suggested by recent optical data on the spatial distribution of rich clusters of galaxies.
Using cosmological models with different values of the spectral index, baryon fraction, Hubble constant, and cosmological
constant, we compare the calculated radiation power spectrum with the CMB temperature anisotropies measured by the Saskatoon
experiment. We show that spectra with a spike at 120h
−1 Mpc are in agreement with the Saskatoon data. The combined evidence from cluster and CMB data favors the presence of a peak
and a subsequent break in the initial matter power spectrum. Such a feature is similar to the prediction of an inflationary
model wherein an inflaton field is evolving through a kink in the potential.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 6, 373–378 (25 September 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
16.
O. V. Kibis 《Journal of Experimental and Theoretical Physics》1999,88(3):527-532
This paper studies the interaction of electrons and acoustic phonons in a quasi-two-dimensional system with an asymmetric
quantizing potential in a magnetic field that is parallel to the structure’s plane. It is demonstrated that the electron-phonon
interaction in such a system generates an emf when there is a standing acoustic wave, as well as when the structure is heated
uniformly. These phenomena are macroscopic manifestations of a universal quantum effect, which amounts to an emf being generated
by any isotropic perturbation of any electron system in which the energy depends asymmetrically on the velocity υ, i.e., ε(υ)≠ε(−υ).
Zh. éksp. Teor. Fiz. 115, 959–969 (March 1999) 相似文献
17.
Experimental investigations and theoretical-model analyses have been made of the magnetooptic diffraction of light at ferrite
garnet magnetic films with a banded domain structure which includes isolated magnetic grating defects in the form of “forks”
and “breaks.” An analysis of the magnetic grating structure and the light diffraction field shows that in terms of its action
on laser radiation, a banded domain grating is similar to a computer-synthesized phase hologram of an isolated pure screw-wavefront
dislocation. It is shown that as a result of magnetooptic diffraction at a magnetic hologram, optical vortices may be reconstructed
with a helicoidal wavefront carrying the topological charge l=±1,±2.
Zh. Tekh. Fiz. 68, 54–58 (December 1998) 相似文献
18.
A vector field q (the order parameter of the molecular packing) describing the packing (specifically, the orientation) of membrane-forming
amphiphilic molecules is introduced to describe the structures of lyotropic phases constructed from membranes. In the general
case q·n≠0 (where n is the unit normal vector) and therefore the singularities of the vector field q are not determined uniquely by the topology of the surface. The condition q·n=0 signifies disruption of the packing of the molecules. This corresponds to holes, which can form in membranes when lyotropic
systems are diluted. As an illustration, the simplest type of such singularities, in which the distribution of the field q around a hole is described by a part of an instanton with unit topological charge, is studied. It is shown that such a distribution
guarantees the existence of a local minimum under the condition that the tension per unit length λ of the hole boundary is small compared with the deformation energy of the field q:
λh/K≪l (K is the modulus of the orientational elasticity of the field q and h is the thickness of the membrane). The radius of the hole which is formed equals L≈2.52(K/λh)1/3 and the energy E≈59.79K(λh/K)1/3.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 8, 575–580 (25 October 1996) 相似文献
19.
The evolution of off-diagonal correlation functions (for the example of a single-particle density matrix) in the process of
Bose condensation of an initially nonequilibrium interacting gas is discussed. Special attention is given to the character
of the decay of the density matrix at distances much greater than the size of the quasicondensate region. Specifically, it
is shown that the exponential decay of the density matrix necessarily presupposes the presence of a chaotic vortex structure
— a tangle of vortex lines — in the system. When topological order is established but there is no off-diagonal long-range
order, the density matrix decays with distance according to a power law.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 495–501 (10 April 1998) 相似文献
20.
G. E. Khodenkov 《JETP Letters》1998,68(11):864-868
As a result of the absence of a definite spatial symmetry in the structure of a 180-degree domain wall in ferromagnets with
negative crystallographic magnetic anisotropy, terms which are even functions of the external driving magnetic field appear
in the velocity of a one-dimensional domain wall, and the wall undergoes drift in an oscillating field.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 11, 823–827 (10 December 1998) 相似文献