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1.
Theoretical studies of the bulk and surface electronic structures of PbBi4Te7 are presented. The PbBi4Te7 compound has a layered structure of five-layer (Bi2Te3) and seven-layer (PbBi2Te4) blocks alternating along the hexagonal axis. Analysis of the spin-orbit-induced inversion of the band gap edges indicates
that this compound is a three-dimensional topological insulator. The topological properties of this compound are mainly determined
by the PbBi2Te4 blocks. The Dirac cone is formed on the PbBi4Te7(0001) surface near the $
\bar \Gamma
$
\bar \Gamma
point for any block (either Bi2Te3 or PbBi2Te4) forming the surface. It is shown that the Dirac state can be localized not only on the surface but also deeply beneath it. 相似文献
2.
Yu. V. Solov’eva S. V. Starenchenko V. A. Starenchenko 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(2):202-206
The creep in Ni3Ge alloy single crystals with strain axis orientations of [001], [$
\bar 1
$
\bar 1
39], [$
\bar 2
$
\bar 2
34], and [$
\bar 1
$
\bar 1
22] was investigated. It was found that changes in strain axis orientation that lead to cubic slip increase the creep resistance
of Ni3Ge alloy single crystals. 相似文献
3.
This study determined the contribution of Martian topography and the density jump at the Mohorovicic discontinuity (M) to the gravity in a quadratic approximation. It also resolved the problem of determining the possible depths of compensation
for topography harmonics of various degrees and orders. It shows that all the topography compensation is within the depth
range from 0 to 1400 km. Different topographic irregularities are most likely to be compensated at depths that correspond
to the upper crust ($
\bar d = 4.5 \pm 3.7{\text{ km}}
$
\bar d = 4.5 \pm 3.7{\text{ km}}
), crust-mantle transition layer ($
\bar d = 78 \pm 24{\text{ km}}
$
\bar d = 78 \pm 24{\text{ km}}
), lithospheric boundary ($
\bar d = 200 \pm 34{\text{ km}}
$
\bar d = 200 \pm 34{\text{ km}}
), upper-middle mantle transition layer ($
\bar d = 400 \pm 70{\text{ km}}
$
\bar d = 400 \pm 70{\text{ km}}
), or middle-lower mantle transition layer ($
\bar d = 1120 \pm 180{\text{ km}}
$
\bar d = 1120 \pm 180{\text{ km}}
). This paper presents the lateral distributions of compensation masses for these depths and the respective maps. According
to calculations, stresses in the Martian crust and mantle may be as high as 108 Pa. This paper shows that the topographic anomalies of the Tharsis volcanic plateau and the symmetric formation in the eastern
hemisphere could have originated and be dynamically maintained by two plumes of melted mantle substance enriched with fluids;
these plumes may have their origin at the boundary of the lower mantle. 相似文献
4.
Spin correlations for the ΛΛ and Λ$
\bar \Lambda
$
\bar \Lambda
pairs, generated in relativistic heavy-ion collisions, and related angular correlations at the joint registration of hadronic
decays of two hyperons, in which space parity is not conserved, are analyzed. The correlation tensor components can be derived
from the double angular distribution of products of two decays by the method of “moments”. The properties of the “trace” of
the correlation tensor (a sum of three diagonal components), determining the relative fractions of the triplet states and
singlet state of respective pairs, are discussed. Spin correlations for two identical particles (ΛΛ) and two nonidentical
particles (Λ$
\bar \Lambda
$
\bar \Lambda
) are considered from the viewpoint of the conventional model of one-particle sources. In the framework of this model, correlations
vanish at sufficiently large relative momenta. However, under these conditions, in the case of two nonidentical particles
(Λ$
\bar \Lambda
$
\bar \Lambda
) a noticeable role is played by two-particle annihilation (two-quark, two-gluon) sources, which lead to the difference of
the correlation tensor from zero. In particular, such a situation may arise when the system passes through the “mixed phase.” 相似文献
5.
The results of the calculation of electron bands of bound states that cross the edge of the continuous spectrum for the (001)
fcc copper monolayer are presented for the first time. The calculations are performed in the local approximation for the exchange
and correlations using the film variant of the Green’s function technique. Symmetry of electron states near the edge of the
continuous spectrum is explored. It is found that there are bound states along the $
\bar \sum
$
\bar \sum
direction of the two-dimensional Brillouin zone of the Cu(001) monolayer that are embedded in the continuum of delocalized
states of the continuous spectrum. Along the $
\bar \Delta
$
\bar \Delta
and $
\bar Y
$
\bar Y
directions, bands of bound states turn into resonance states after crossing the edge of the continuous spectrum. 相似文献
6.
K. S. Aleksandrov S. V. Misyul M. S. Molokeev V. N. Voronov 《Physics of the Solid State》2009,51(12):2505-2512
The structures of all three phases of the Rb2KInF6 crystal have been determined from the experimental X-ray diffraction data for the powder sample. The refinement of the profile
and structural parameters has been carried out by the technique implemented in the DDM program, which minimizes the differences
between the derivatives of the calculated and measured X-ray intensities over the entire profile of the X-ray diffraction
pattern. The results obtained have been discussed using the group-theoretical analysis of the complete order-parameter condensate,
which takes into account the critical and noncritical atomic displacements and permits the interpretation of the experimental
data obtained previously. It has been reliably established that the sequence of changes in the symmetry during phase transitions
in Rb2KInF6 can be represented as $
Fm\bar 3m\xrightarrow[{0,0,\phi }]{{11 - 9\left( {\Gamma _4^ + } \right)}}{{I114} \mathord{\left/
{\vphantom {{I114} {m\xrightarrow[{\left( {\psi ,\phi ,\phi } \right)}]{{11 - 9\left( {\Gamma _4^ + } \right) \oplus 10 - 3\left( {X_3^ + } \right)}}{{P12_1 } \mathord{\left/
{\vphantom {{P12_1 } {n1}}} \right.
\kern-\nulldelimiterspace} {n1}}}}} \right.
\kern-\nulldelimiterspace} {m\xrightarrow[{\left( {\psi ,\phi ,\phi } \right)}]{{11 - 9\left( {\Gamma _4^ + } \right) \oplus 10 - 3\left( {X_3^ + } \right)}}{{P12_1 } \mathord{\left/
{\vphantom {{P12_1 } {n1}}} \right.
\kern-\nulldelimiterspace} {n1}}}}
$
Fm\bar 3m\xrightarrow[{0,0,\phi }]{{11 - 9\left( {\Gamma _4^ + } \right)}}{{I114} \mathord{\left/
{\vphantom {{I114} {m\xrightarrow[{\left( {\psi ,\phi ,\phi } \right)}]{{11 - 9\left( {\Gamma _4^ + } \right) \oplus 10 - 3\left( {X_3^ + } \right)}}{{P12_1 } \mathord{\left/
{\vphantom {{P12_1 } {n1}}} \right.
\kern-\nulldelimiterspace} {n1}}}}} \right.
\kern-\nulldelimiterspace} {m\xrightarrow[{\left( {\psi ,\phi ,\phi } \right)}]{{11 - 9\left( {\Gamma _4^ + } \right) \oplus 10 - 3\left( {X_3^ + } \right)}}{{P12_1 } \mathord{\left/
{\vphantom {{P12_1 } {n1}}} \right.
\kern-\nulldelimiterspace} {n1}}}}
. 相似文献
7.
M. N. Zakharenkov 《Thermophysics and Aeromechanics》2009,16(3):391-396
The known problem of flow transition near a circular cylinder at Re = 40 from a symmetrical form to the Karman vortex street
can be considered as the problem of vortex wave development and intensification. Development of three bundles of vortex waves
of low intensity is observed in a wake of a cylinder; these bundles are easily visualized as the structures of relative vorticity
$
\bar \Omega
$
\bar \Omega
= Ω(t
1) − Ω(t
0): difference of vorticity Ω at two time moments, t
0 being fixed. In the field of $
\bar \Omega
$
\bar \Omega
the alternating structure of quadrupoles is characterized by linear parameter l = h/d: the ratio of the width of the central bundle of vortex waves to the distance between the centers of quadrupoles of a “single
sign”. When l = 0.281 is achieved, which coincides with the value of the same parameter of a stable Karman street, the transition from
symmetrical streamlining by viscous incompressible liquid to the vortex street occurs. 相似文献
8.
V. P. Ruban 《Journal of Experimental and Theoretical Physics》2010,111(5):776-785
We consider slow, compared to the speed of sound, motions of an ideal compressible fluid (gas) in a gravitational field in
the presence of two isentropic layers with a small specific-entropy difference between them. Assuming the flow to be potential
in each of the layers (v
1, 2 = ▿ϕ1, 2) and neglecting the acoustic degrees of freedom (div($
\bar \rho
$
\bar \rho
(z)▿ϕ1, 2) ≈ 0, where $
\bar \rho
$
\bar \rho
(z) is the average equilibrium density), we derive the equations of motion for the boundary in terms of the shape of the surface
z = η(x, y, t) itself and the difference between the boundary values of the two velocity field potentials: ψ(x, y, t) = ψ1 − ψ2. We prove the Hamilto nian structure of the derived equations specified by a Lagrangian of the form ℒ = ∫$
\bar \rho
$
\bar \rho
(η)η
t
ψdxdy − ℋ{η, ψ}. The system under consideration is the simplest theoretical model for studying internal waves in a sharply stratified
atmosphere in which the decrease in equilibrium gas density due to gas compressibility with increasing height is essentially
taken into account. For plane flows, we make a generalization to the case where each of the layers has its own constant potential
vorticity. We investigate a system with a model dependence $
\bar \rho
$
\bar \rho
(z) ∝ e
−2αz
with which the Hamiltonian ℋ{η, ψ} can be represented explicitly. We consider a long-wavelength dynamic regime with dispersion
corrections and derive an approximate nonlinear equation of the form u
t
+ auu
x
− b[−$
\hat \partial _x^2
$
\hat \partial _x^2
+ α2]1/2
u
x
= 0 (Smith’s equation) for the slow evolution of a traveling wave. 相似文献
9.
We present the measurement of directed flow (v
1) for the identified particles, namely, Λ, $
\bar \Lambda
$
\bar \Lambda
and K
s
0, as a function of rapidity and centrality in Au+Au collisions at $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 200 GeV and 62.4 GeV. The measurement is based on the run IV data obtained by the STAR experiment at RHIC. In order to
enhance event plane resolution, we use tracks reconstructed from the Forward Time Projection Chambers (FTPCs), together with
the sideward deflection of spectator neutrons measured by the STAR’s Shower Maximum Detector at Zero Degree Calorimeters (ZDC-SMDs).
We find that for 200 GeV, proton and antiproton v
1 is less than 1%, the K
s
0
Λ, $
\bar \Lambda
$
\bar \Lambda
v
1 is less than 2%; for 62 GeV, proton v
1 is less than 1% and antiproton is less than 2%, v
1 for K
s
0, Λ, $
\bar \Lambda
$
\bar \Lambda
is less than 2% in Au+Au collisions at 200 GeV. 相似文献
10.
E. A. Vopilkin V. I. Shashkin Yu. N. Drozdov V. M. Daniltsev A. Yu. Klimov V. V. Rogov I. Yu. Shuleshova 《Technical Physics》2009,54(10):1476-1480
A microelectromechanical system is created that has the form of a cantilever-fitted microbar with a cross-sectional area of
several square micrometers. The system is formed by applying epitaxial AlGaAs layers on the GaAs(001) surface and selective
chemical etching of the AlAs layer lying under the bar. Two micro-cantilevers that are made on the same GaAs(001) wafer and
directed along the [110] and [1$
\bar 1
$
\bar 1
0] orthogonal diagonal axes are studied. The static and dynamic characteristics of the systems are studied by white light
optical interferometry. The deflection of the bars as a function of the applied voltage is measured in the static mode. An
opposite shift of orthogonal microcantilevers on which the same voltage is applied is considered as direct evidence of the
efficiency of a piezoeffect-based microengine. The calculated parameters of the micro-electromechanical system, the sensitivity
and eigenfrequency, are in good agreement with the measurements. 相似文献
11.
R. N. Kyutt M. P. Shcheglov V. V. Ratnikov A. E. Nikolaev 《Physics of the Solid State》2009,51(9):1789-1795
The structural state of GaN epitaxial layers grown on r-plane sapphire through metal-organic vapor phase epitaxy has been investigated using X-ray diffraction. The interplanar spacings
in two directions in the (11$
\bar 2
$
\bar 2
0) plane of the interface and in the direction perpendicular to it, as well as the diffraction peaks in the ϑ and ϑ-2ϑ scan
modes in the Bragg and Laue geometries, are measured on double- and triple-crystal diffractometers. The intensity distribution
maps for asymmetric Bragg reflections are constructed for two azimuthal positions of the sample. An analysis of the data obtained
has demonstrated that the elastic strain is anisotropic and that the X-ray diffraction pattern parallel to the interface plane
is broadened. The layers are contracted in the [1$
\bar 1
$
\bar 1
00] direction and unstrained in the [0001] direction. The broadening of the Bragg reflections in the [1$
\bar 1
$
\bar 1
00] direction is considerably larger than that in the [0001] direction. It is shown using the Williamson-Hall plots for the
Bragg and Laue reflections that these broadenings are not related to different degrees of mosaicity but are determined by
the local dilatations and misorientations around defects. The data obtained are analyzed, and the conclusions regarding the
dislocation structure of the samples are drawn. 相似文献
12.
We have obtained inequality $
1 - {{\Delta \bar \tau } \mathord{\left/
{\vphantom {{\Delta \bar \tau } {\bar \tau }}} \right.
\kern-\nulldelimiterspace} {\bar \tau }} < \left( {J \cdot V \cdot \bar \tau } \right)^{ - 1} < 1 + {{\Delta \bar \tau } \mathord{\left/
{\vphantom {{\Delta \bar \tau } {\bar \tau }}} \right.
\kern-\nulldelimiterspace} {\bar \tau }}
$
1 - {{\Delta \bar \tau } \mathord{\left/
{\vphantom {{\Delta \bar \tau } {\bar \tau }}} \right.
\kern-\nulldelimiterspace} {\bar \tau }} < \left( {J \cdot V \cdot \bar \tau } \right)^{ - 1} < 1 + {{\Delta \bar \tau } \mathord{\left/
{\vphantom {{\Delta \bar \tau } {\bar \tau }}} \right.
\kern-\nulldelimiterspace} {\bar \tau }}
, where J is the frequency of homogeneous nucleation, V and $
\bar \tau
$
\bar \tau
are, respectively, volume and average lifetime of the superheated liquid, and $
{{\Delta \bar \tau } \mathord{\left/
{\vphantom {{\Delta \bar \tau } {\bar \tau }}} \right.
\kern-\nulldelimiterspace} {\bar \tau }}
$
{{\Delta \bar \tau } \mathord{\left/
{\vphantom {{\Delta \bar \tau } {\bar \tau }}} \right.
\kern-\nulldelimiterspace} {\bar \tau }}
is relative statistical error $
\bar \tau
$
\bar \tau
. Inequality appears to be a consequence of nucleation homogeneity and stability used at its deduction and taken in the theory
as initial and determinant assumption. Calculations with the use of experimental data for the boundaries of the attainable
superheating show that inequality is not satisfied. Thus, experimental data can not be considered a proof of the theory fundamentals. 相似文献
13.
Utilizing the Baym-Kadanoff formalism with the polarization function calculated in the random phase approximation, the dynamics
of the ν = 0 quantum Hall state in bilayer graphene is analyzed. Two phases with nonzero energy gap, the ferromagnetic and
layer asymmetric ones, are found. The phase diagram in the plane ($
\bar \Delta _0
$
\bar \Delta _0
, B), where $
\bar \Delta _0
$
\bar \Delta _0
is a top-bottom gates voltage imbalance, is described. It is shown that the energy gap scales linearly, ΔE ∼ 14B [T] K, with magnetic field. 相似文献
14.
Yu. S. Surovtsev T. Branz T. Gutsche V. E. Lyubovitskij 《Physics of Particles and Nuclei》2010,41(6):990-993
In a model-independent approach the data on ππ → ππ, K
$
\bar K
$
\bar K
, ηη, ηη′ in the I
G
J
PC
= 0+0++ channel and on the Kπ scattering in the $
I\left( {J^P } \right) = \frac{1}
{2}\left( {0^ + } \right)
$
I\left( {J^P } \right) = \frac{1}
{2}\left( {0^ + } \right)
channel are analyzed jointly for studying the status and QCD nature of the f
0- and the K*0-mesons. It is shown that in the 1500-MeV region, there are two states, wide (interpreted as a glueball) and narrow (q
$
\bar q
$
\bar q
). In the Kπ-scattering data analysis, the proof for the K*0(900) is given. 相似文献
15.
G. H. Arakelyan A. B. Kaidalov C. Merino Yu. M. Shabelski 《Physics of Atomic Nuclei》2011,74(3):426-436
The WA89 Collaboration experimental data on production of Λ, Σ−, Σ+, Ξ−, Ω− baryons, $
\bar \Lambda
$
\bar \Lambda
and $
\bar \Xi ^ +
$
\bar \Xi ^ +
antibaryons in Σ− collisions with C and Cu targets at 345 GeV/c ($
\sqrt {s_{\Sigma N} }
$
\sqrt {s_{\Sigma N} }
≈ 25.5 GeV) in the frame of the Quark-Gluon String Model is described. The comparison of the theoretical results with the
experimental data is discussed. Finally, some relations among the values of the model parameters obtained with the help of
quark combinatorics are presented. 相似文献
16.
17.
The structures of two phases of the (NH4)3Nb(O2)2F4 crystal, namely, the parent cubic phase and the most distorted low-temperature phase, have been determined from data of an
X-ray diffraction experiment performed for a powder sample. The profile and structural parameters have been refined according
to the procedure implemented in the DDM program. The results obtained have been discussed with invoking the group-theoretical
analysis of the complete order parameter condensate, which takes into account the critical and noncritical atomic displacements
and allows the interpretation of the obtained experimental data. It has been found that the most probable sequence of structural
transformations occurring in the crystal can be schematically represented in the following form:
_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose] _5^ + (11 - 7)C2/mP2_1 /m | #xA; P2_1 /n. | #xA; |
#xA;\begin{gathered}
Fm\bar 3m\xrightarrow[{(\eta 1,\eta 1,\eta )}]{{\Gamma _5^ + (11 - 7)}}C2/m\xrightarrow[{(\eta 1,\eta 1,\eta )(0,0,0,0,0,\xi ,0 - \xi ,0,0,0,0)}]{{\Gamma _5^ + (11 - 7) \otimes \Sigma _2 (4 - 2)}}P2_1 /m \hfill \\
\xrightarrow[{(\eta 1,\eta 1,\eta )(0,0,0,0,0,\xi ,0 - \xi ,0,0,0,0)(0,0,0,0,0,\varepsilon ,0,\varepsilon ,0,0,0,0)}]{{\Gamma _5^ + (11 - 7) \otimes \Sigma _2 (4 - 2) \otimes \Sigma _3 (4 - 3)}}P2_1 /n. \hfill \\
\end{gathered}
相似文献
18.
Measuring the $
\bar \nu _e
$
\bar \nu _e
component of the cosmic diffuse supernova neutrino background (DSNB) is the next ambitious goal for low-energy neutrino astronomy.
The largest flux is expected in the lowest accessible energy bin. However, for E ≲ 15 MeV a possible signal can be mimicked by a solar $
\bar \nu _e
$
\bar \nu _e
flux that originates from the usual 8B neutrinos by spin-flavor oscillations. We show that such an interpretation is possible within the allowed range of neutrino
electromagnetic transition moments and solar turbulent field strengths and distributions. Therefore, an unambiguous detection
of the DSNB requires a significant number of events at E ≳ 15 MeV. 相似文献
19.
D. V. Shirkov 《Physics of Particles and Nuclei Letters》2010,7(6):379-383
The dimensional reduction, in a form of transition from four to two dimensions, was used in the 90s of the past century in
a context of the HE Regge scattering. Recently, it has got a new impetus in quantum gravity where it opens the way to renormalizability
and finite short-distance behaviour. We consider a QFT model gφ4 with running coupling defined in both domains of different dimensionality; the $
\bar g
$
\bar g
(q
2) evolutions being duly correlated at the reduction scale q ∼ M. Beyond this scale, in the deep UV 2-dimensional region, the running coupling does not increase any more. Instead, it slightly
decreases and tends to a finite value $
\bar g
$
\bar g
2(∞) < $
\bar g
$
\bar g
2(M
2) from above. As a result, the global evolution picture looks quite peculiar and proposes a base for the modified scenario
of gauge couplings behavior with UV fixed points provided by dimensional reduction instead of leptoquarks. 相似文献
20.
A. I. Dmitriev V. M. Kaminski G. V. Lashkarev P. E. Butorin Z. D. Kovalyuk V. I. Ivanov A. I. Beskrovny 《Physics of the Solid State》2009,51(11):2342-2346
The neutron diffraction patterns have been analyzed for a layered single crystal and a powder of the γ-polytype of indium
selenide in the temperature range 10–300 K. In the temperature range 10–50 K, the excitation of bending vibrations due to
the charge density waves changes the phonon spectrum and gives rise to a negative thermal expansion in the plane of layers,
i.e., α‖c
= −2.2 × 10−6 K−1, which is characteristic of two-dimensional structures. The average (over the range T = 50–300 K) coefficients of thermal expansion along the principal crystallographic directions have been calculated: $
\bar \alpha _{ \bot c}
$
\bar \alpha _{ \bot c}
= 10.48 × 10−6 K−1 and $
\bar \alpha _{\parallel c}
$
\bar \alpha _{\parallel c}
= 12.97 × 10−6 K−1, which agree with the X-ray diffraction data previously obtained by the authors at T = 290 K. 相似文献
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