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1.
M. A. Krasil’nikov M. V. Kuzelev A. A. Rukhadze 《Journal of Experimental and Theoretical Physics》1997,85(4):705-711
A theoretical and numerical analysis is made of the dynamics of nonlinear electron-beam scattering of a wave reflected by
the emitting device of a plasma oscillator. It is shown that a counterpropagating plasma wave can interact nonlinearly with
other waveguide modes of the system and with charge-density beam waves, leading to changes in the operation of the oscillator.
It is established by means of a numerical simulation that the generation efficiency is reduced as a result of scattering of
the counterpropagating wave and stimulated emission of a strong-potential plasma wave with phase velocity v
ph=ω/k
z≪c.
Zh. éksp. Teor. Fiz. 112, 1299–1311 (October 1997) 相似文献
2.
A. A. Verevkin N. G. Ptitsina K. V. Smirnov G. N. Gol’tsman E. M. Gershenzon K. S. Ingvesson 《JETP Letters》1996,64(5):404-409
The temperature dependence of the energy relaxation time τe (T) of a two-dimensional electron gas at an AlGaAs/GaAs heterointerface is measured under quasiequilibrium conditions in the
region of the transition from scattering by acoustic phonons to scattering with the participation of optical phonons. The
temperature interval of constant τe, where scattering by the deformation potential predominates, is determined. In the preceding, low-temperature region, where
piezoacoustic and deformation-potential-induced scattering processes coexist, τ e decreases slowly with increasing temperature. Optical phonons start to participate in the scattering processes at T∼25 K (the characteristic phonon lifetime was equal to τLOτ4.5 ps). The energy losses calculated from the τe data in a model with an effective nonequilibrium electron temperature agree with the published data obtained under strong
heating conditions.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 371–375 (10 September 1996) 相似文献
3.
Optical nutation at the Raman-active transition 6P
1/2−6P
3/2 of thallium atoms (ω
R
/2πc=7793 cm −1) under resonant Raman excitation by a biharmonic picosecond pulsed field, giving rise to substantial motion of the population,
is detected. Optical nutation appears as an oscillatory behavior of the energy of the anti-Stokes scattering of probe pulses,
which follow with a fixed delay, as a function of the product of the energies of the excitation pulses. As a result of the
dynamic Stark effect, which decreases the frequency of the transition under study, resonance excitation conditions are satisfied
for negative initial detunings of the Raman excitation frequency from resonance. The Raman scattering cross section for the
transition under study is estimated by comparing the experimental data with the calculations.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 1, 7–12 (10 July 1999) 相似文献
4.
A study is reported of the thermoelectric and galvanomagnetic properties of n-Bi2Te3−x−y
SexSey solid solutions for 0.12⩽x⩽0.36 and 0.12⩽y⩽0.21 within the 80–300 K temperature region. The thermoelectric figure-of-merit Z has been found to correlate with the parameters of the many-valley energy-band model including anisotropic carrier scattering.
It is shown that a decrease in the constant-energy surface anisotropy and scattering anisotropy results in a growth of Z for optimum carrier concentrations in the solid solution.
Fiz. Tverd. Tela (St. Petersburg) 41, 187–192 (February 1999) 相似文献
5.
Guang S. He Yiping Cui Paras N. Prasad 《Journal of Experimental and Theoretical Physics》1997,85(5):850-856
The spectral structure of backward stimulated scattering from a 10 cm-long CS2-liquid cell is investigated by using Q-switched 10-ns and 532-nm laser pulses with different spectral linewidths. Under a narrow spectral line (∼0.1 cm−1) pump condition, very strong sharp lines near the pump wavelength (λ
0) position and the first-order stimulated Raman scattering (λ
s1) position can be observed. However, under a wide line (≈1 cm−1) pump condition, only a strong and superbroadening spectral band can be observed mainly in the red-shift side of the pump
wavelength. The different spectral features under these two conditions can be explained by a competition between stimulated
Brillouin, Raman, and Rayleigh-Kerr scattering. Under both pump conditions, the broadening spectral distributions are not
consistent with the predictions given by stimulated Rayleigh-wing scattering theories, but can be interpreted well utilizing
the theoretical model of stimulated Rayleigh-Kerr scattering.
Zh. éksp. Teor. Fiz. 112, 1563–1573 (November 1997)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
6.
Thermoelectric power in quasi-two-dimensional systems with scattering of current carriers by phonons
B. M. Askerov B. I. Guliev S. R. Figarova I. R. Gadirova 《Physics of the Solid State》1997,39(10):1659-1660
The thermopower α in electron systems with a quasi-two-dimensional energy spectrum is investigated in the relaxation-time tensor approximation.
The longitudinal and transverse components of the thermopower are calculated for scattering of the current carriers by different
types of phonons. It is shown that the anisotropy of the thermopower in such systems is substantial. The dependence of a on
the ratio of the Fermi level ɛ
F to the half-width ɛ
0 of the one-dimensional conduction band is considered. For scattering by acoustical and nonpolar optical phonons, the thermopower
changes sign: α becomes positive for ɛ
F<ɛ
0. Comparison of the theory with published experimental data demonstrates good qualitative agreement.
Fiz. Tverd. Tela (St. Petersburg) 39, 1857–1858 (October 1997) 相似文献
7.
J. Becker H.G. Andresen J.R.M. Annand K. Aulenbacher K. Beuchel J. Blume–Werry Th. Dombo P. Drescher M. Ebert D. Eyl A. Frey P. Grabmayr T. Großmann P. Hartmann T. Hehl W. Heil C. Herberg J. Hoffmann J.D. Kellie F. Klein K. Livingston M. Leduc M. Meyerhoff H. Möller Ch. Nachtigall A. Natter M. Ostrick E.W. Otten R.O. Owens S. Plützer E. Reichert D. Rohe M. Schäfer H. Schmieden R. Sprengard M. Steigerwald K.-H. Steffens R. Surkau Th. Walcher R. Watson E. Wilms 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):329-344
The electric form factor of the neutron GEn has been determined in double polarized exclusive 3
He(e,e'n) scattering in quasi–elastic kinematics by measuring asymmetries A
⊥, A
∥ of the cross section with respect to helicity reversal of the electron, with the nuclear spin being oriented perpendicular
to the momentum transfer q in case of A⊥ and parallel in case of A∥. The experiment was performed at the 855 MeV c. w. microtron MAMI at Mainz. The degree of polarization of the electron beam
and of the gaseous 3
He target were each about 50%. Scattered electrons and neutrons were detected in coincidence by detector arrays covering large
solid angles. Quasi–elastic scattering events were reconstructed from the measured electron scattering angles ϑe, φe and the neutron momentum vector p
n
′ in the plane wave impulse approximation. We obtain the result <G
En>(0.27 < Q2c2/GeV2 < 0.5)= 0.0334 ± 0.0033stat± 0.0028syst which is averaged over the indicated range of Q
2, the squared momentum transfer. This G
En value is significantly smaller than measured from the D(e,e'n) reaction under similar kinematical conditions. To what extent final state interactions in 3He quench the G
En result is subject of calculations currently in progress elsewhere.
Received: 29 April 1999 相似文献
8.
9.
J.C. Lasjaunias P. Monceau D. Starešinić K. Biljaković 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):187-190
Eur. Phys. J. B 24, 315 (2001) In our Reply to the Comment [#!1!#] we refute the “straightforward” interpretation of the excess low-temperature
specific heat, Cp, contribution we have measured in our study of CDW systems K0.3MoO3 and (TaSe4)2I [#!2!#] as originating solely from normal phonon modes. The specific sensitivity of the bump in C
p
/
T
3
at low temperatures to the impurity content is consistent with the increased value of the phason pinning gap while the dispersion
of normal phonons remains unaffected. We ascribe at least this part of the anomaly to the phason contribution. As stated in
reference [3] that the phonon density of states extracted from neutron scattering measurements is the least reliable in this
energy range (<0.5 meV), we conclude that Cp measurements are more accurate for detecting the phason contribution.
Received 17 April 2002 Published online 19 July 2002 相似文献
10.
Raman scattering of light by optical phonons in Si-Ge-Si structures with pseudomorphic germanium quantum dots has been investigated.
Resonance amplification of the scattering intensity on E
0 (Γ7−Γ8) transitions has been observed. It is shown that as a result of the formation of the layer of germanium quantum dots, the
resonance energy is ∼0.3 eV higher than in the two-dimensional case.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 203–207 (10 August 1996) 相似文献
11.
G. I. Harus A. N. Ignatenkov N. K. Lerinman A. I. Ponomarev L. D. Sabirzyanova N. G. Shelushinina N. A. Babushkina L. M. Belova 《JETP Letters》1996,64(6):444-449
The temperature and magnetic-field dependences of the resistivity ρ and Hall effect R(j‖ab, B‖c) in a Nd1.82Ce0.18CuO4−δ
single crystal film (T
c
=6 K) is investigated at temperatures 1.4≤T≤20 K and magnetic fields 0≤B≤5.5 T. At the lowest temperature T=1.4 K the resistive state (exhibiting resistivity and the Hall effect) arises in a magnetic field B=0.5 T. A transition to the normal state is completed at B
c
2≃3 T, where the Hall coefficient becomes nearly constant. The negative magnetoresistance due to the weak-localization effect
in the normal state is observed for B>3 T. The nonmonotonic behavior and the inversion of the sign of R(B) in the mixed state are explained in a reasonable way by the flux-flow model with the effect of pinning taken into account.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 6, 407–411 (25 September 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
12.
The energy gap appearing in the spin-wave spectrum as a result of Bragg scattering by the modulation period q=2π/(d
1+d
2) of a one-dimensional superlattice is observed by the method of spin-wave resonance in Co/Pd multilayer films. It is shown
that this gap is asymmetric: The “positive” deviation is from two to three times greater than the “negative” deviation.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 938–941 (25 June 1996) 相似文献
13.
A new method is proposed for setting a lower or upper limit a α
n
* on the neutron electric polarizability α
an
. It is based on the fact that the real part of the s-wave scattering amplitude changes sign near the s-wave neutron resonance at E=E*. The methods consist of the observation of the energy behavior of the forward-backward scattering asymmetry ω
1 which experiences a jump at E=E*. If the jump is such that dω
1/dE>0, then α
n
>α
n
*, while if dω
1/dE<0, then α
n
<α
n
*, and if dω
1/dE∼0, then α
n
∼α
n
*. Seven even-even nuclei are found with α
n
* from 0.5 to 3.1 in 10−3 fm3. Some details of a possible experiment with 182W are described.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 3, 171–174 (10 August 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
14.
S. I. Krasnosvobodtsev N. P. Shabanova V. S. Nozdrin A. I. Golovashkin 《Physics of the Solid State》1999,41(8):1256-1259
The high-temperature superconductors YBa2Cu3O7−δ
, HoBa2Cu3O7−δ
, and Nd1.85Ce0.15CuO4−δ
are found to possess a common anomaly in the variation of the upper critical magnetic field owing to irradiation by helium
ions. While the resistivity ρ increases by many times, the increase in H
c2 from scattering by radiation defects typical of ordinary superconductors does not occur. In terms of the ordinary mechanism,
the anomaly may be explained by a significant reduction in the conduction electron density resulting from a loss of oxygen,
which causes a significant rise in ρ with a small change in the scattering.
Fiz. Tverd. Tela (St. Petersburg) 41, 1372–1376 (August 1999) 相似文献
15.
I. G. Kuleev A. T. Lonchakov I. Yu. Arapova G. I. Kuleev 《Journal of Experimental and Theoretical Physics》1998,87(1):106-114
A new effect of the reduction in the rate of phonon scattering by the spatially correlated system of iron ions in HgSe:Fe
crystals is detected experimentally and calculated theoretically. The thermoelectric power is measured using HgSe:Fe samples
with different iron content in the temperature range 7.5–60 K. It is found that the dependence of the thermoelectric power
on iron content exhibits remarkable features at T<10 K: the quantity |α(N
Fe
)| increases as the iron concentration increases to N
Fe
=5×1018 cm−3, reaches a maximum at N
Fe
≈(1–2)×1019 cm−3, but then monotonically decreases with further increases in N
Fe
. It is shown that the obseved increase in the thermoelectric power is due to a reduction in the rate of phonon scattering
by the spatially correlated system of Fe3+ ions. This new effect is analyzed theoretically, and the theoretical results are compared with the experimental data.
Zh. éksp. Teor. Fiz. 114, 191–207 (July 1998) 相似文献
16.
R. N. Kyutt 《Physics of the Solid State》1997,39(7):1052-1056
Double-and triple-crystal diffractometry have been used to study structural perfection of a ∼1 μm-thick Ga1−x
InxSb1−y
Asy epitaxial film (x=0.9, y=0.8) on GaSb. It is shown that scattering from samples of this system can be divided into coherent and diffuse. The arrangement
of reciprocal-lattice points of the film and substrate in the two-dimensional intensity distribution for asymmetrical reflections
argues for the absence of elastic-strain relaxation. No dislocation networks are formed, and the diffuse scattering is produced
by Coulomb-type defects. Localization of diffuse scattering in reciprocal space suggests that these defects reside in the
epitaxial film. The diffuse-scattering distribution in asymmetrical reflections is shown to be anomalous; namely, it extends
in a direction parallel to the surface and is split into two maxima. Schemes have been proposed and realized for measuring
integral distributions of diffracted intensity along the surface and perpendicular to it, and their potential for studying
diffuse scattering from defects is explored.
Fiz. Tverd. Tela (St. Petersburg) 39, 1188–1193 (July 1997) 相似文献
17.
S. V. Grigor’ev S. A. Klimko S. V. Maleev A. I. Okorokov V. V. Runov D. Yu. Chernyshov 《Journal of Experimental and Theoretical Physics》1997,85(6):1168-1179
A magnetic phase transition in carbon-doped (0.1 and 0.7 at. %) Fe70Ni30 Invar alloys was investigated by the method of depolarization of a transmitted neutron beam and by small-angle scattering
of polarized neutrons. It is shown that for both alloys, two characteristic length scales of magnetic correlations coexist
above T
c. Small-angle scattering by critical correlations with radius R
c is described well by the Ornstein-Zernike (OZ) expression. The longer-scale (second) correlations, whose size can be estimated
from depolarization data, are not described by the OZ expression, and hypothetically can be modeled by a squared OZ expression,
which in coordinate space corresponds to the relation 〈M(r)M(0)〉∝exp(−r/R
d), where R
d is the correlation length of the second scale. The temperature dependence of the correlation radius R
c was obtained: R
c ∝ ((T−T
c)/Tc)−ν
, where ν≈2/3 is the critical exponent for ferromagnets, over a wide temperature range up to T
c
exp
, at which the correlation radius becomes constant and equals its maximum value R
c(T
c)=R
c
max
. The maximum correlation radius established (R
c
max
=140 Å and 230 Å for the first and second alloys, respectively) characterizes the length-scale of the fluctuation for which
the appearance of critical correlations first results in the formation of a ferromagnetic phase, and the phenomenon itself
exhibits a “disruption” of the second-order phase transition at T=T
c
exp
, as a result of which a first-order transition arises. Temperature hysteresis was also detected in the measured polarization
of the transmitted beam and intensity of small-angle neutron scattering in the alloy above T
c, confirming the character of this magnetic transition as a first-order transition close to a second-order transition.
Zh. éksp. Teor. Fiz. 112, 2134–2155 (December 1997) 相似文献
18.
A computational scheme based on the infinite order sudden approximation (IOS) is proposed for treating molecular and screening
effects in muonic atom scattering at low energies. With this scheme the differential (dσ/dΩ(ɛj← 0|θ) and the total σtot(ɛ) cross-sections of muonic atom scattering on molecules of hydrogen isotopes are calculated at energies ɛrot=ℏωI⩽ɛ⩽ɛvib= ℏω03BD;. The IOS permits a quantitative analysis of the dependence of the differential cross-sections on the scattering angle and
on the rotational excitations, particularly the rotational rainbow effects. An attractive feature of this approach is also
to include the energy and the angular dependencies in the “input” cross-sections describing the muonic atom scattering on
each bare nucleus of the molecule. The calculated total cross-sections ωtot(ɛ) are in agreement with the data obtained earlier with the pseudopotential approach.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
A. V. Vedyaev A. B. Granovskii A. V. Kalitsov F. Brouers 《Journal of Experimental and Theoretical Physics》1997,85(6):1204-1210
A theoretical study is performed of the anomalous Hall effect in granular alloys with giant magnetoresistance. The calculation
is carried out within the Kubo formalism and the Green’s function method. The mechanism of asymmetric scattering of the spin-polarized
current carriers is considered with allowance for a size effect associated with scattering not only by one grain, but also
with more complicated processes of transport among two and three grains. It is shown that scattering of conduction electrons
by the interfaces of the grains and the matrix has a substantial effect on the magnitude of the anomalous Hall effect and
determines its sign. In general, correlation between the quantities ρ
H and ρ
2 is absent, where ρ
H is the Hall resistivity and ρ is the total resistivity of the granular alloy. However, numerical calculation shows that for certain values of the model
parameters ρ
H∼ρ
3.8 and for these same parameter values the amplitude of the giant magnetoresistance reaches 40%, which is found to be in quantitative
agreement with the experimental data for Co20Ag80 alloys [P. Xiong, G. Xiao, J. Q. Wang et al., Phys. Rev. Lett. 69, 3220 (1992)]. It is also shown that increasing the resistivity of the matrix leads to a significant growth in the anomalous
Hall effect, and more substantial growth for alloys with small grain size, which is in good agreement with experiment [A.
B. Pakhomov, X. Yan, and Y. Xu, J. Appl. Phys. 79, 6140 (1996); [X. N. Jing, N. Wang, and A. B. Pakhomov, Phys. Rev. B 53, 14032 (1996)].
Zh. éksp. Teor. Fiz. 112, 2198–2209 (December 1997) 相似文献
20.
We study the resistive properties of 3D normal-metal-superconductor systems in the pure mean-free-path limit l
N,S
≫ξ(T) (l
N,S
are the mean free paths in the metals, and ξ is the coherence length) at liquid helium temperatures. In contrast to the situation where l≪ξ, which is common in experiments involving either sandwiches or mesoscopic samples, here the N-S system exhibits unusual temperature behavior that cannot be described by existing theories of boundary resistance. What is
most remarkable is a rise in normal resistance in regions that do not incorporate the N-S boundary as the temperature decreases, with asymptotic behavior resembling that of the temperature curve of the gap of a
superconductor in contact with a normal metal. We show that this effect, not observed earlier in 3D systems, is due to the
nonequivalence of the cross sections of scattering by normal-metal impurities of electron and hole excitations in conditions
of Andreev reflection. We also show that in standard measurements of the contribution of the N-S boundary lying between the test contacts, this effect is masked by accompanying effects, the proximity effect and the boundary
resistance, whose estimate requires taking into account the presence on the N-S boundary of an electrostatic barrier of the Schottky type, a barrier that redistributes the probabilities of ordinary and
Andreev reflections of quasiparticles in the nonequilibrium conditions due to current flow.
Zh. éksp. Teor. Fiz. 113, 1064–1070 (March 1998) 相似文献