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1.
E. A. Shapoval 《JETP Letters》1999,69(8):577-583
The lower critical field H
c1
cyl
(T) of a superconducting cylinder with radius r
0∼ξ(T)≪λ(T) is found on the basis of the Ginzburg-Landau theory with various boundary conditions. These results together with the well-known
results for the upper critical field are used to construct phase diagrams in terms of the field versus the reduced radius
r
0∼ξ(T) variables. The jump in the average magnetization at H
c1
cyl
(T) is calculated as a function of the reduced radius.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 8, 537–542 (25 April 1999) 相似文献
2.
The annihilation of the nematic hedgehog and anti-hedgehog within an infinite cylinder of radius R is studied. The semi-microscopic lattice-type model and Brownian molecular dynamics are used. We distinguish among the i)
early pre-collision, ii) late pre-collision, iii) early post-collision, and iv) late post-collision stages. In the pre-collision stage our results agree qualitatively with the existing experimental observations and also continuum-type simulations. The
core of each defect exhibits a ring-like structure, where the ring axis is set perpendicular to the cylinder symmetry axis. For ξ(0)d/(2R) > 1 the interaction between defects is negligible, where ξ(0)d describes the initial separation of defects. Consequently, the defects annihilate within the simulation time window for ξ(0)d/(2R) < 1. For close enough defects their separation scales as ξd
(tc - t)0.4±0.1, where tc stands for the collision time. In elastically anisotropic medium the hedgehog is faster than the anti-hedgehog. In the early pre-collision stage the defects can be treated as point-like particles, possessing inherent core structure, that interact via the nematic director field. In the late pre-collision stage the cores reflect the interaction between defects. After the collision a charge-less ring structure is first formed. In the early post-collision stage the ring adopts an essentially untwisted circular structure of the radius ξr. In the late post-collision stage we observe two qualitatively different scenarios. For μ = ξr/R < μc ∼ 0.25 the ring collapses leading to the escaped radial equilibrium structure. For μ > μc the chargeless ring triggers the nucleation growth into the planar polar structure with line defects. 相似文献
3.
Evgeni Korotyaev 《Communications in Mathematical Physics》2000,213(2):471-489
The spectral properties of the Schr?dinger operator T(t)=−d
2/dx
2+q(x,t) in L
2(ℝ) are studied, where the potential q is defined by q=p(x+t), x>0, and q=p(x), x<0; p is a 1-periodic potential and t∈ℝ is the dislocation parameter. For each t the absolutely continuous spectrum σ
ac
(T(t))=σ
ac
(T(0)) consists of intervals, which are separated by the gaps γ
n
(T(t))=γ
n
(T(0))=(α
n
−,α
n
+), n≥1. We prove: in each gap γ
n
≠?, n≥ 1 there exist two unique “states” (an eigenvalue and a resonance) λ
n
±(t) of the dislocation operator, such that λ
n
±(0)=α
n
± and the point λ
n
±(t) runs clockwise around the gap γ
n
changing the energy sheet whenever it hits α
n
±, making n/2 complete revolutions in unit time. On the first sheet λ
n
±(t) is an eigenvalue and on the second sheet λ
n
±(t) is a resonance. In general, these motions are not monotonic. There exists a unique state λ0(t) in the basic gap
γ0(T(t))=γ0(T(0))=(−∞ ,α0
+). The asymptotics of λ
n
±(t) as n→∞ is determined.
Received: 5 April 1999 / Accepted: 3 March 2000 相似文献
4.
Summary It is shown that the behaviour of the temperature dependence of the critical current in polycrystalline thin films of high-T
c superconductors depends crucially on the assumption made concerning the nature of the intergranular material. The usual assumption
of a superconductor-insulator-superconductor (=SIS) ?sandwich? between each grain leads to a crossover fromI
c∼(1−T/T
c) toI
c∼(1−T/T
c)3/2, for temperatures nearT
c (whereI
c is the critical current,T the absolute temperature, andT
c the superconducting transition temperature). Instead, for a superconductor-normal metal-superconductor (=SNS) sandwich the
dependenceI
c∼(1−T/T
c)2 is found for all temperatures. Consideration is given to the effect of self-magnetic field on the analysis. The comparison
between expressions for continuous and granular systems is extended.
Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction. 相似文献
5.
Evidence that pinning on linear or planar defects dominates the vortex dynamics in YBa2Cu3O7−x (YBCO) films is provided by complex impedance measurements at temperature 8 K<T<T
c
and magnetic field 0<B<6 T. Below the vortex lattice melting transition Bg(T) but above a threshold field Bp≈8(1-T/T
c
) T, the inductance of vortices increases as B2, much less rapidly than predicted for collective pinning of vortices by point defects. Above the vortex melting line, critical
scaling persists over the region Bg(T<B<B*(T) where the vortex correlation length ξ exceeds a characteristic length scale ξ*≡ξ(B=B*)≈450?. The value of ξ* is not sensitive to Al-doping in the Cu sites in the lattice and is close to the size of twin domains in the film. The nature
of the observed crossovers is discussed in terms of available theoretical models for a glass-liquid transition at Bg. 相似文献
6.
Y. Tao G. Bergmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(1):42
The Friedel oscillations in the vicinity of a Friedel-Anderson (FA) impurity are investigated numerically. For an FA impurity
in the local moment limit the normalized amplitude A(ξ) is S-shaped, approximately zero at short distances, approaching two at large distances and crossing the value one at the
characteristic length ξ
1/2. Surprisingly, the Friedel oscillations of a simple non-interacting Friedel impurity with a narrow resonance at the Fermi
level show a very similar behavior of their amplitude A(ξ). A comparison correlates the resonance width and the Kondo energy of the FA impurity with the characteristic length ξ
1/2 of the Friedel oscillations. 相似文献
7.
Nariyuki Minami 《Communications in Mathematical Physics》2000,213(1):203-247
Let f(ϕ) be a positive continuous function on 0 ≤ϕ≤Θ, where Θ≤ 2 π, and let ξ be the number of two-dimensional lattice points in
the domain Π
R
(f) between the curves r=(R+c
1/R)f(ϕ) and r=(R+c
2/R)f(ϕ), where c
1<c
2 are fixed. Randomizing the function f according to a probability law P, and the parameter R according to the uniform distribution μ
L
on the interval [a
1
L,a
2
L], Sinai showed that the distribution of ξ under P×μ
L
converges to a mixture of the Poisson distributions as L→∞. Later Major showed that for P-almost all f, the distribution of ξ under μ
L
converges to a Poisson distribution as L→∞. In this note, we shall give shorter and more transparent proofs to these interesting theorems, at the same time extending
the class of P and strengthening the statement of Sinai.
Received: 15 June 1999 / Accepted: 11 February 2000 相似文献
8.
N. N. Achasov 《JETP Letters》1996,63(8):601-606
It is shown that BR(χ
b1(1 P)→e
+
e
−)≃3.3· 10−7 and BR(χ
c1(1 P)→e
+
e
−)≃10−8. This gives realistic possibilities for searching for the production of χ
b1(1 P) and ξ
c1(1 P) states in e
+
e
− collisions, even on the present-day colliders, to say nothing of b and c-τ factories.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 569–574 (25 April 1996) 相似文献
9.
Current-voltage (J-V) and differential-conductivity-voltage ( dJ/dV-V) characteristics are analytically calculated at zero temperature for a point contact consisting of: two Peierls conductors
P
( = 1, 2) separated by an insulator (I). Here P is a conductor with charge density wave (CDW). The J-V and dJ/dV-V characteristics depend on the CDW phases ( = 1, 2) in the mean field approximation. To calculate them analytically we assumed, = ≡Δ where ( = 1, 2) are the energy gaps of P
( = 1, 2). The current J has a discontinuous jump at eV = 2Δ for ϕ
1 = ϕ
2≠ 0. The differential conductivity dJ/dV has a singularity at eV = 2Δ for ϕ
1 = ϕ
2≠ 0. The relation J(V,ϕ
1,ϕ
2) = - J(- V,ϕ
1 + π,ϕ
2 + π) is obtained.
Received 4 July 2001 and Received in final form 13 September 2001 相似文献
10.
Hanqin Ding Yanshen Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(2):169-175
Using the deformed Hubbard operator approach, we analytically study weak-coupling phase diagram of the one-dimensional t-J-V model at half filling. In the case of small deformed parameter ζ(≪1), the interactions induced by the no double occupancy constraint are softened, accessible by the bosonization field theory
and the renormalization group technique. The ground state exhibits insulating behavior of density-wave correlations. The bond-spin-density-wave
(BSDW) and
bond-charge-density-wave (BCDW) phases are realized in the whole weak-coupling regime while the charge-density-wave (CDW)
and spin-density-wave (SDW) phases depend on V/J > (V/J)
c
or V/J < (V/J)
c
, where (V/J)
c
= 1/4. Furthermore, our results are expected to adiabatically continue back to ζ = 1. 相似文献
11.
M. A. Zelikman 《Physics of the Solid State》1997,39(11):1751-1755
A system of pancake vortices formed near the boundary of a sample in a monotonically increasing external magnetic field is
calculated with allowance for pinning due to the cellular structure of the medium for various values of the pinning parameter
I, which is proportional to the critical current of the junction and the cell diameter. The shortest distance from the outermost
vortex to the nearest neighbor is proportional to I
−11. It is shown that the pinning parameter has a critical value I
c separating two regimes with different types of critical states. For I<I
c the external magnetic field has a threshold value H
t(I), above which the field immediately penetrates the interior of the junction to an infinite distance. For I>I
c the magnetic field decays linearly from the boundary into the interior of the junction. The value obtained in the study,
I
c=3.369, differs from the value of 0.9716 postulated by other authors. The dependence of the slope of the magnetic field profile
near the boundary on I is determined. It is shown that the slope is independent of I in intervals 2πk<I<2πk+π.
Fiz. Tverd. Tela (St. Petersburg) 39, 1958–1963 (November 1997) 相似文献
12.
13.
A. A. Snarskii K. V. Slipchenko I. V. Bezsudnov 《Journal of Experimental and Theoretical Physics》1998,86(4):811-814
An exact relation for the realization-averaged effective conductivities in the fractal region is found for two-dimensional
randomly inhomogeneous media. It has the form {σ
e
(τ,L)~× {1/σ
e
(−τ,L)~−1=σ
e
2
(τ=0, L≫ξ), where ξ is the correlation length (the self-averaging scale), L is the size of the system, τ=(p-p
c
)/p
c
, and p
c
is the percolation threshold. For L≫ ξ, the system is self-averaged, and the relation transforms into the Dykhne reciprocity relation, A. M. Dykhne, Zh. éksp. Teor.
Fiz. 59, 110 (1970) [Sov. Phys. JETP 32, 63 (1971)] σ
e
(τ)σ
e
(−τ])=σ
e
2
(τ=0)= σ
1
σ
2. A similar relation is obtained for media with an exponentially broad distribution of local conductivities, as well as for
individual realizations of some deterministic structures.
Zh. éksp. Teor. Fiz. 113, 1484–1490 (April 1998) 相似文献
14.
N. O. Agasian 《JETP Letters》2012,95(4):171-175
The nonperturbative QCD vacuum at finite temperature and baryon density in an external magnetic field has been studied. Relations
between the nonperturbative condensates and the thermodynamic pressure at T ≠ 0, μ
q
≠ 0, and H ≠ 0 have been obtained and the low-energy theorems have been derived. Bulk viscosity ζ(T, μ, H) has been described in terms of the main thermodynamic quantities characterizing the quark-gluon matter at T ≠ 0, μq ≠ 0, and H ≠ 0. Various limiting cases have been discussed. 相似文献
15.
A. D. Bianchi E. Felder A. Schilling M. A. Chernikov F. Hulliger H. R. Ott 《Zeitschrift für Physik B Condensed Matter》1995,99(1):69-76
We report measurements of the specific heatC
p(T), electrical resistivity ϱ(T) and magnetic susceptibility ξ(T) of hexagonal CePd2In, at low temperatures. Anomalies inC
p(T), χ(T) and ϱ(T) atT=1.23 K, indicate a phase transition, most likely to an antiferromagnetically-ordered phase. The electronic entropy reachesR ln2 per mole Ce at 9.2K, suggesting that the phase transition involves a doublet state. The ordered phase coexists with moderately
correlated itinerant electrons. 相似文献
16.
CHEN JiSheng QIN Fang & WANG YanPing Physics Department Central China Normal University Wuhan China 《中国科学G辑(英文版)》2009,52(9):1324-1329
A quasi-Gaussian approximation scheme is formulated to study the strongly correlated imbalanced Fermions thermodynamics, where
the mean-field theory is not applicable. The non-Gaussian correlation effects are understood to be captured by the statistical
geometric mean of the individual susceptibilities. In the three-dimensional unitary fermions ground state, a universal nonlinear
scaling transformation relates the physical chemical potentials with the individual Fermi kinetic energies. For the partial
polarization phase separation to full polarization, the calculated critical polarization ratio is δ
C = [1−(1−ξ)6/5]/[1+(1−ξ)6/5] ≐ 0.34. ξ = 4/9 gives the ratio of the symmetric ground state energy density to that of the ideal fermion gas.
Supported by the National Natural Science Foundation of China (Grant Nos. 10875050 and 10675052), the Fund of Central China
Normal University, and the Foundation of Ministry of Education of China (Grant No. IRT0624) 相似文献
17.
M. A. Zelikman 《Technical Physics》2009,54(2):197-203
A new approach to magnetic field profiling inside a Josephson contact is suggested. Its essence consists in analyzing continuous
variation of a current configuration leading to a decrease in the Gibbs potential. With this approach, one can find a configuration
into which the Meissner state turns when an external field slightly exceeds the upper boundary of the Meissner regime and
trace the evolution of this configuration with increasing field. Calculations show that there exists critical value I
c of the pinning parameter in the range 0.95–1.00. This critical value separates two possible conditions of magnetic field
penetration into the contact. At I > I
c, a near-boundary current configuration completely compensating for the external field inside the contact arises irrespective
of the external field strength. At I < I
c, such a situation is observed only until the external field strength exceeds certain value H
max. Higher fields penetrate into the contact indefinitely deep. In nearboundary configurations, the magnetic field drops with
increasing depth almost linearly. Its slope k has rational values, which remain constant within finite intervals of I. As I goes beyond a given interval, k rises stepwise and takes on another rational value. When an external magnetic field is switched on adiabatically, configurations
with a maximal growth rate of the magnetic field are observed. 相似文献
18.
V. V. Anisovich L. G. Dakhno M. A. Matveev V. A. Nikonov A. V. Sarantsev 《Physics of Atomic Nuclei》2007,70(2):364-381
Earlier by the authors (Yad. Fiz. 70, 68 (2007)), the bƃ states were treated in the framework of the spectral integral equation, together with simultaneous calculations of radiative
decays of the considered bottomonia. In the present paper, such a study is carried out for the charmonium
states. We reconstruct the interaction in the c-c sector on the basis of the data for the charmonium levels with J
PC = 0−+, 1−−, 0++, 1++, 2++, 1+− and radiative transitions ψ(2S) → γχ
c0(1P), γχ
c1(1P), γχ
c2(1P), γχ
c(1S) and χ
c0(1P), χ
c1(1P), χ
c2(1P) → γJ/ψ. The c-c levels and their wave functions are calculated for the radial excitations with n ≤ 6. Also, we determine the c-c component of the photon wave function using the e
+
e
−-annihilation data: e
+
e
− → J/ψ(3097), ψ(3686), ψ(3770), ψ(4040), ψ(4160), ψ(4415) and perform the calculations of the partial widths of the two-photon decays for the n = 1 states η
c0(1S), χ
c0(1P), χ
c2(1P) → γγ and n = 2 states η
c0(2S) → γγ, χ
c0(2P) → γγ. We discuss the status of the recently observed c-c states X(3872) and Y(3941): according to our results, the X(3872) can be either χ
c1(2P) or η
c2(1D), while Y(3941) is χ
c2(2P).
The text was submitted by the authors in English. 相似文献
19.
The excited state absorption upconversion of Pr(0.5)Yb(3):ZBLAN glass material, under two-color excitation of the 960 nm semiconductor
laser and the Xe lamp light simultaneously, is reported in this article. It was found that the upconversion emission spectra
of 480.1, 519.0, 601.9 and 631.8 nm coincide with the common emission spectra. Meanwhile, the upconversion-excitation spectrum
has three obvious peaks under two-color excitation, and they respectively correspond to the 856.0 nm upconversion excitation
transition [1G4(Pr3+)→1I6(Pr3+) and 1G4(Pr3+)→3P1(Pr3+)], the 789.0 nm upconversion excitation transition 1G4(Pr3+)→3P2(Pr3+), and the 803.7 nm upconversion excitation transition 3H6(Pr3+)→1D2(Pr3+). The upconversion excitation transition 1G4(Pr3+)→1I6(Pr3+) is strong because its oscillator strength f = 23.040×10−6 is large, which results in a large peak appearing in the upconversion excitation spectrum. That is just the new interesting
two-color excitation upconversion luminescence phenomenon of Pr(0.5)Yb(3):ZBLAN induced by one laser and one continuous normal
light simultaneously. 相似文献
20.
A new model of electronic vortices in plasma is studied. The model assumes that the profile of the Lagrangian invariant I, equal to the ratio I=Ω/n of the electronic vorticity to the electron density, is given. The proposed approach takes into account the magnetic Debye
scale r
B
≃B/4πen, which leads to breakdown of plasma quasineutrality. It is shown that the Abrikosov singular model cannot be used to describe
electron vortices in plasmas because of the fundamental limitation on the electron vorticity on the axis of a vortex in a
plasma. Analysis of the equations shows that in the model considered for the electronic vorticity, the total magnetic flux
decreases when the size r
0 of the region in which I≠0 becomes less than c/ωpe (ωpe is the electron plasma frequency). For ω
pe
r
0/c≪1, an electronic vortex is formed in which the magnetic flux decreases as r
0
2
and the inertial component predominates in the electronic vorticity. The structure arising as ω
pe
r
0/c⇒0 is a narrow “hole” in the electron density, which can be identified from the spectrum of electromagnetic waves in this
region.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 461–466 (10 April 1998) 相似文献