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1.
The nonadiabatic corrections to the self-energy part Σs(q, ω) of the phonon Green’s function are studied for various values of the phonon vectors q resulting from electron-phonon interactions. It is shown that the long-range electron-electron Coulomb interaction has no
direct influence on these effects, aside from a possible renormalization of the corresponding constants. The electronic response
functions and Σs(q, ω) are calculated for arbitrary vectors qand energy ω in the BCS approximation. The results obtained for q=0 agree with previously obtained results. It is shown that for large wave numbers q, vertex corrections are negligible and Σs(q, ω) possesses a logarithmic singularity at ω=2Δ, where Δ is the superconducting gap. It is also shown that in systems with nesting, Σs(Q, ω) (where Q is the nesting vector) possesses a square-root singularity at ω=2Δ, i.e., exactly of the same type as at q=0. The results are used to explain the recently published experimental data on phonon anomalies, observed in nickel borocarbides
in the superconducting state, at large q. It is shown, specifically, that in these systems nesting must be taken into account in order to account for the emergence
of a narrow additional line in the phonon spectral function S(q, ω)≈−π
−1 Im D
s
(q, ω), where D
s
(q, ω) is the phonon Green’s function, at temperatures T<T
c
.
Zh. éksp. Teor. Fiz. 115, 1799–1817 (May 1999) 相似文献
2.
The correlation of the local density of states 〈ρɛ(r
1)ρɛ + ω(r
2)〉 in quasi-one-dimensional disordered wires in a magnetic field is calculated under the assumption that |r
1 − r
2| is much smaller than the localization length. This amounts to finding the zero mode of the transfer-matrix Hamiltonian for
the supersymmetric σ model, which is done exactly by mapping to the three-dimensional Coulomb problem. Both the regimes of
level repulsion and level attraction are obtained, depending on |r
1 − r
2|. We demonstrate that the correlations of different eigenfunctions in the quasi-one-dimensional and strictly one-dimensional
cases are dissimilar.
The text was submitted by the authors in English. 相似文献
3.
N. A. Silant’ev 《Journal of Experimental and Theoretical Physics》1999,89(1):45-55
In this paper the procedure of large-scale averaging of the magnetic-field diffusion equation with the α-term curlα(r,t)B(r,t) is used to show that a nonuniform distribution of the turbulent helicity fluctuations (more precisely, the fluctuations
of the coefficient α) with a zero average value gives rise to large-scale amplification of the initial magnetic field. A detailed study is carried
out of the dependence of the resulting large-scale α effect on the characteristics of the correlator 〈〈α(r, t)α(r″,t″)〉〉 in a rotating medium with a nonuniform distribution of the angular velocity ω=ω(ρ,z) (ρ is the distance for the rotation axis z). The effect of helicity fluctuations and the diffusion coefficient on the turbulent diffusion process is also investigated.
Zh. éksp. Teor. Fiz. 116, 85–104 (July 1999) 相似文献
4.
L. I. Buravov 《Russian Physics Journal》2009,52(1):25-32
Masses of a number of elementary particles are calculated on the basis of the model suggested in [1] with the use of one parameter. In this model, an electron is considered as an electric cloud enclosed inside an elastic
lepton shell, electron neutrino ν
е
is considered as an elastic lepton shell contracted to a minimal size, and muon, pion and kaon are considered as resonators
for quanta of virtual neutrinos excited inside the elastic lepton shell. The number and type of these quanta are determined
from the decay scheme for μ, π, and K: 2 for the muon (ν
е
and ), 3 for the pion (ν
е
,
ν
μ, and ), and at least 21 for the kaon. The model allows mass ratios approximating the experimental data for these particles to be
obtained for the first time, with the ratio of μ and е masses equal to (6πℏс/е
2)2/3 ≅ 188, the ratio of π
0 and μ masses equal to (3/2)2/3, and the ratio of K
0 and π
0
equal masses to 72/3. The calculated e, μ
,
π
0, and K
0 masses are in the 0.547:105.707:134.963:493.87 (MeV) ratios (normalized by the neutral pion mass). This is in good agreement
with the available experimental data. The mass ν
е
(≅ 0.02 eV) is also estimated in this model, and the variety of K-meson decay schemes is naturally explained as a result of the variety of excited intrinsic neutrino field structures with
the same energy.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 23–29, January, 2009. 相似文献
5.
A. I. Alekseev 《Journal of Experimental and Theoretical Physics》1997,84(1):35-50
The properties of the density matrix and the multipole moments arising in oriented and aligned atoms with zero nuclear spin
through the interaction with strong resonant ultrashort pulses with wave vector k
0 and circular or linear polarization have been found. Calculations have been made for the time-dependent light-induced magnetization
μ(t′) of a gas of pre-oriented and prealigned atoms following the passage of a weak resonant elliptically polarized pulse with
frequency ω and wave vector k collinear with k
0. It is shown that for oriented atoms, μ(t′) is an even function of the detuning from resonance, ω-ω
ba, and can be split into two terms whose directions are a consequence of symmetry and are determined by the vectors k
0 and k as well as by the direction of rotation of the electric fields corresponding to the pulses. For aligned atoms the vector
μ(t′) is collinear with k, and the first term is an even function of ω-ω
ba. However, the second term is an odd function of ω-ω
ba and reverses direction when the sign of ω-ω
ba changes, as well as when the orientation of the axes of the polarization ellipse is changed. It is shown that if a series
of weak linearly polarized pulses pass through the gas, the light-induced magnetization of the oriented and aligned gas atoms
can be decomposed into three factors: the first determines the direction and is a consequence of the symmetry; the second
(with the dimensions of magnetic moment) depends on the characteristics of the resonant transitions; and the third is a universal
function of t′ and ω-ω
ba that does not depend on the underlying characteristics of the resonant transition. These vector factors and the universal
functions are in principle different for oriented and aligned atoms.
Zh. éksp. Teor. Fiz. 111, 63–92 (January 1997) 相似文献
6.
P. Boubert P. Vervisch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):43-48
Excitation of carbon monoxide molecules has been carried out in a cold cell and in a low-pressure plasma jet using an ArF
narrow-band excimer laser. The different excitation models are discussed and the relevance of atomic carbon absorption into
the laser cavities is pointed out. Excitation spectra of Cameron bands have been obtained in a room-temperature cell and compared
with calculated spectra. A value of the constant σ related to the interaction strength between a
3
Π(
v
= 2) state and its neighbouring singlet states is derived: 0≤σ≤0.05. The fluorescence spectrum following broad band excitation of CO has been observed both in UV and visible. Similar experiments
carried out in a high enthalpy flow have allowed to point out the presence of a
3
Π metastable carbon monoxide. A method for relative measurements of this species concentration is proposed.
Received 9 April 2001 and Received in final form 13 June 2001 相似文献
7.
B. A. Grinberg M. A. Ivanov O. V. Antonova A. M. Vlasova N. A. Kruglikov A. V. Plotnikov 《Russian Physics Journal》2012,54(8):906-913
The self-blocking effect predicted theoretically and then observed in intermetallides is established for a pure metal, namely,
for magnesium. This effect can be observed only for magnesium single crystals whose axis is parallel to the c axis and whose yield stress behavior σ
y
(T) has a temperature anomaly. For such single crystals, the self-blocking of the (c + a)-type edge dislocations is established during pyramidal slip of type II. The self-blocking is proved by dislocation extension
along the preferred direction without external stress. In this case, the
á 1[`1]00
ñ \left\langle {1\bar{1}00} \right\rangle directions appear preferred. TEM images of (c + a) dislocations extended along the preferred directions are presented. It is demonstrated that two effects – temperature anomaly
of σ
y
(T) and dislocation self-blocking – have the common nature: a two-valley potential relief of the dislocation. A model of two-valley
relief of the (c + a) dislocations in Mg is proposed. 相似文献
8.
M. Celasco R. Eggenhöffner 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):415-419
A dynamical percolative model explaining the universality of 1/
f
γ
noise is reported. Exponents γ ranging from 0 to 2 are obtained under the hypothesis that noise originates from random switching events between two ON-OFF
states in elemental parts (switchers) of a physical system. The usual noise behaviour with γ very close to 1 in an arbitrarily wide frequency range is obtained assuming a statistical distribution of switcher relaxation
time τ proportional to τ
-1
, as in McWhorter's model. The impact of these results with respect to recent self-organised criticality models is discussed.
Received 6 November 2000 and Received in final form 22 May 2001 相似文献
9.
O. V. Kibis 《JETP Letters》1997,66(8):588-593
In low-dimensional systems with an asymmetric quantizing potential, an asymmetric electron energy spectrum ε(p)≠ε(−p), where p is the electron momentum, arises in the presence of a magnetic field. A consequence of such an energy spectrum is that momentum
transfer to the electron system in mutually opposite directions in the presence of an external perturbation is different.
Therefore, in the presence of a standing electromagnetic wave momentum is transferred from the wave to the electrons, which
gives rise to a new type of electromotive force.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 551–555 (25 October 1997) 相似文献
10.
11.
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
12.
The damping γ(ε) of electron states in crystals is investigated beyond the phase transition point related to a rearrangement
of the Fermi surface. Attention is focused on the alteration of the standard Landau theory due to the emergence of a flat
portion in the spectrum ξ(p) of single-particle excitations as a result of the rearrangement. In the limit ε →0, the width γ(ε) of the states in the
region of the Brillouin zone where the dispersion of ξ(p) is of an ordinary order of magnitude is found to depend on ε almost linearly, in contrast to the Fermi-liquid-theory result
γ(ε)∼ε2.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 759–765 (10 December 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
13.
An explicit solution is obtained for the four-wave mixing ω4=ω1−ω 2+ω3 of two strong fields E
1, E
3 and two weak fields E
2, E
4 in a four-level system with large Doppler broadening. Resonance of the intensity dependence of the mixing coefficient is
found around equal Rabi frequencies, E
1·d
1=E
3·d
3, where d
1,3 are the dipole moments of the corresponding transitions. The effect is interpreted as a crossing of quasi-energy levels.
Up to 6 peaks appear in the dependence of the conversion coefficient on the detuning of the probe field E
2. The unexpected additional pair of peaks is a consequence of averaging over velocities. The results permit interpretation
of the saturation behavior found in recent experiments on mixing in sodium vapor.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 777–782 (25 December 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
14.
It is shown that the degeneracy of the noncanonical Poisson bracket operating on the space of solenoidal vector fields that
arises due to the freezing-in of the curl of the velocity [E. A. Kuznetsov and A. V. Mikhailov, Phys. Lett. A 77, 37 (1980)] is lifted when the vorticity Ω is represented in terms of vortex lines. This representation makes it possible
to integrate the equation of motion of the vorticity for a system with the Hamiltonian H=∫∣Ω∣d
r.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 12, 1015–1020 (25 June 1998) 相似文献
15.
N. Shramchenko F. Dénoyer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):51-59
A detailed investigation of the Fourier space of several Al-Pd-Mn samples with composition Al-72.6 at. %, Pd-22.9 at. %, Mn-4.5
at. % is reported. In the phase diagram of the Al-Pd-Mn ternary alloy, this composition corresponds to the so-called ξ' phase which was described as an icosahedral quasicrystalline approximant. By re-examining the Fourier space by means of
X-ray diffraction (powder patterns and single crystal precession patterns), complex structures in close relation with the
ξ'-phase have been observed. These long-range order complex structures are described as resulting from a periodic perturbation
of the ξ' structure along the c direction. Two states with periodicities c
(3 + τ) and c
(5 + τ) have been observed in this study (τ: golden mean). Structural models based on periodic arrangements of “defects” layers separating layers of phase are proposed. These two states are certainly intermediate states between the phase and the metastable decagonal quasicrystalline phase.
Received 11 April 2002 / Received in final form 24 June 2002 Published online 17 September 2002 相似文献
16.
Krzysztof Rȩbilas 《Foundations of Physics Letters》2006,19(4):337-351
The Coulomb force, established in the rest frame of a source-charge Q, when transformed to a new frame moving with a velocity V has a form F = q
E + q
v × B, where E = E′∥ + γE′⊥ and B = (1/c
2)v × E and E′ is the electric field in the rest frame of the source. The quantities E and B are then manifestly interdependent. We prove that they are determined by Maxwell's equations, so they represent the electric
and magnetic fields in the new frame and the force F is the well known from experiments Lorentz force. In this way Maxwell's equations may be discovered theoretically for this
particular situation of uniformly moving sources. The general solutions of the discovered Maxwell's equations lead us to fields
produced by accelerating sources. 相似文献
17.
The possibility of resonance during elastic intravalley scattering in n-type semiconductors is investigated in connection with the crossing (due to anisotropy of the effective mass) of the energy
levels of excited states of a shallow donor as functions of the magnetic field. The hybridization of states of different frequencies
in the vicinity of a crossing is attributed to the emergence of a nonzero dipole moment of the excited impurity atom and,
accordingly, a long-range potential, which creates carrier-transport anomalies. The lower part of the donor spectrum is calculated
as a function of the magnetic field in Si with B∥〈001〉 and in Ge with B∥〈111〉 or B∥〈110〉. A crossing occurs in Ge in the field range 9.9 T<B<16.7 T and in Si in the field range 10.5 T<B<37.7 T. The characteristic longitudinal relaxation time and the transverse conductivity, which are determined by scattering
at excited donors in the presence of the hybridization of states, are calculated.
Zh. éksp. Teor. Fiz. 112, 975–1010 (September 1997) 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.
H. Gayvallet J.-C. Géminard 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):369-375
We have studied the temperature dependent resistivity ρ(
T
) of La2-xSrxCuO4 epitaxial thin films in the doping range 0.045 ⩽
x
⩽ 0.25 in pulsed magnetic fields up to 50 T. The zero-field resistivity ρ(
T
) of these samples in the pseudogap regime, can be scaled onto one single universal curve in a broad temperature range by using
a linear transformation of both temperature and resistivity. The high field data ρ(
T
) reveal a metal to insulator transition (MIT) at low temperatures, well into the overdoped regime. For samples having k
F
l
< 1, with kF the Fermi wave vector and l the mean free path, this low temperature insulating behavior of the resistivity is described by the variable range hopping
conductivity (VRH). For samples with k
F
l
> 1, the divergence follows ρ(
T
) ∼
ln
(1/
T
) or a power law, depending upon the Sr-content. We further found that the residual conductivity at the minimum in ρ(
T
), appearing due to the MIT, follows a linear behavior with respect to the Sr-content. It is argued that the unusual MIT in
compounds with k
F
l
> 1, is most probably associated with the pseudogap and the behavior of charge stripes at low temperatures.
Received 4 January 2002 / Received in final form 7 May 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: liesbet.weckhuysen@fys.kuleuven.ac.be 相似文献
20.
P. Descouvemont 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):413-419
The 9Be and 9B nuclei are investigated in a microscopic three-cluster model involving α + α +
n (or α + α +
p) configurations. The 8Be (0
+
, 2
+
) +
n and 5He (3/2
-
, 1/2
-
) + α (or mirror) channels are included by taking account of the unstable nature of 8Be and 5He. Spectroscopic properties of 9Be and 9B are analyzed. We show that the 5He + α configurations cannot be neglected to derive accurate results. The 9Be(γ,αα)n photodisintegration cross-section is shown to be mainly determined by 8Be + n channels at low energies, but 5He + α channels become important beyond E
γ≈ 4 MeV.
Received: 7 September 2001 / Accepted: 19 November 2001 相似文献