共查询到20条相似文献,搜索用时 31 毫秒
1.
P. Schwab R. Raimondi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):5-8
We consider non-equilibrium transport in disordered conductors. We calculate the interaction correction to the current for
a short wire connected to electron reservoirs by resistive interfaces. In the absence of charging effects we find a universal
current-voltage-characteristics. The relevance of our calculation for existing experiments is discussed as well as the connection
with alternative theoretical approaches.
Received 2 September 2002 Published online 29 October 2002 相似文献
2.
M. Giroud K. Hasselbach H. Courtois D. Mailly B. Pannetier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):103-109
We present electrical transport experiments performed on submicron hybrid devices made of a ferromagnetic conductor (Co) and
a superconducting (Al) electrode. The sample was patterned in order to separate the contributions of the Co conductor and
of the Co-Al interface. We observed a strong influence of the Al electrode superconductivity on the resistance of the Co conductor.
This effect is large only when the interface is highly transparent. We characterized the dependence of the observed resistance
decrease on temperature, bias current and magnetic field. As the differential resistance of the ferromagnet exhibits a non-trivial
asymmetry, we claim that the magnetic domain structure plays an important role in the electron transport properties of superconducting
/ ferromagnetic conductors.
Received 9 July 2002 / Received in final form 22 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: herve.courtois@grenoble.cnrs.fr
RID="b"
ID="b"associated to Université Joseph Fourier 相似文献
3.
B. Lamine M.-T. Jaekel S. Reynaud 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):165-176
We study the decoherence of atomic interferometers due to the scattering of stochastic gravitational waves. We evaluate the
“direct” gravitational effect registered by the phase of the matter waves as well as the “indirect” effect registered by the
light waves used as beam-splitters and mirrors for the matter waves. Considering as an example the space project HYPER, we
show that both effects are negligible for the presently studied interferometers.
Received 15 February 2002 / Received in final form 12 April 2002 Published online 19 July 2002 相似文献
4.
Xin-Hai Liu Xue-Hua Wang Ben-Yuan Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):339-342
We investigate the effects of spatial asymmetry, tunneling coupling, and exchange-correlation correction on the plasmon modes
in asymmetric double quantum well (DQW) structures in a time-dependent local-density approximation. Special attention is paid
to the properties of the ω
- mode which is always damped in symmetric DQW systems. In addition, the results on the spectral weight of the excitations
are also presented. In general, all the modes carry finite spectral weights and should be observable in resonant inelastic
light scattering experiments for the specified values of the parameters.
Received 2 July 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: c412-1@aphy.iphy.ac.cn 相似文献
5.
We discuss the adsorption of polymer gels on flat surfaces. Even in cases of complete wetting where the spreading power S is positive and where an equivalent liquid would spread, the elastic stresses due to the gel deformation upon adsorption
oppose the spreading. The competition between elasticity characterized by the bulk shear modulus G and capillarity characterized by the spreading power S defines a typical length scale ℓ = S/G for the deformation in the gel. For loose gels ℓ can be of the order of 1 μm. Macroscopic gels larger than ℓ deform only
at their edges over a region of size ℓ. Microscopic gels smaller than ℓ show a finite deformation despite the elastic stresses.
The elastic stresses limit the spreading of the polymer, but solvent can be sucked out of a swollen gel by wetting the surface.
The thin solvent film can extend rather far from the gel edge and carry solvent. We calculate the kinetics of the solvent
film formation and of the solvent transfer from a more swollen gel to a less swollen gel.
Received 16 July 2001 相似文献
6.
B.S. Kandemir T. Altanhan 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):517-526
We investigate the stability condition of large bipolarons confined in a parabolic potential containing certain parameters
and a uniform magnetic field. The variational wave function is constructed as a product form of electronic parts, consisting
of center of mass and internal motion, and a part of coherent phonons generated by Lee-Low-Pines transformation from the vacuum.
An analytical expression for the bipolaron energy is found, from which the ground and excited-state energies are obtained
numerically by minimization procedure. The bipolaron stability region is determined by comparing the bipolaron energy with
those of two separate polarons, which is already calculated within the same approximation. It is shown that the results obtained
for the ground state energy of bipolarons reduce to the existing works in zero magnetic field. In the presence of a magnetic
field, the stability of bipolarons is examined, for three types of low-dimensional system, as function of certain parameters,
such as the magnetic-field, the electron-phonon coupling constant, Coulomb repulsion and the confinement strength. Numerical
solutions for the energy levels of the ground and first excited states are examined as functions of the same parameters.
Received 7 March 2002 and Received in final form 22 April 2002 Published online 25 June 2002 相似文献
7.
C.M. Horowitz E.V. Albano 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):563-569
The relationship between a microscopic parameter p, that is related to the probability of choosing a mechanism of deposition, and the stochastic equation for the interface's
evolution is studied for two different models. It is found that in one model, that is similar to ballistic deposition, the
corresponding stochastic equation can be represented by a Kardar-Parisi-Zhang (KPZ) equation where both λ and ν depend on
p in the following way: ν(p) = νp and λ(p) = λp
3/2. Furthermore, in the other studied model, which is similar to random deposition with relaxation, the stochastic equation
can be represented by an Edwards-Wilkinson (EW) equation where ν depends on p according to ν(p) = νp
2. It is expected that these results will help to find a framework for the development of stochastic equations starting from
microscopic details of growth models.
Received 26 August 2002 / Received in final form 20 November 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: ealbano@inifta.unlp.edu.ar 相似文献
8.
9.
S. Franke-Arnold S.M. Barnett G. Huyet C. Sailliot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):373-383
We analyse the coherence properties of two particles trapped in a one-dimensional harmonic potential. This simple model allows
us to derive analytic expressions for the first and second order coherence functions. We investigate their properties depending
on the particle nature and the temperature of the quantum gas. We find that at zero temperature non-interacting bosons and
fermions show very different correlations, while they coincide for higher temperatures. We observe atom bunching for bosons
and atom anti-bunching for fermions. When the effect of s-wave scattering between bosons is taken into account, we find that the range of coherence is enhanced or reduced for repulsive
or attractive potentials, respectively. Strongly repelling bosons become in some way more “fermion-like" and show anti-bunching.
Their first order coherence function, however, differs from that for fermions.
Received 19 September 2002 Published online 4 February 2003 相似文献
10.
D.C. Cabra G.L. Rossini 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):529-532
We study the breaking of parity symmetry in the 2+1 Gross-Neveu model at finite temperature with chemical potential μ, in
the presence of an external magnetic field. We find that the requirement of gauge invariance, which is considered mandatory
in the presence of gauge fields, breaks parity at any finite temperature and provides for dynamical mass generation, preventing
symmetry restoration for any non-vanishing μ. The dynamical mass becomes negligibly small as temperature is raised.
Received 4 April 2002 / Received in final form 12 July 2002 Published online 15 October 2002
RID="a"
ID="a"e-mail: cabra@venus.fisica.unlp.edu.ar 相似文献
11.
G. Savona D.V. Livanov A.A. Varlamov 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):415-420
We study the fluctuation-induced magnetotransport of a two-dimensional superconductor in the quasiballistic regime, where
ξ
GL(T) ≪ ℓ (ℓ is the electron mean free path and ξ
GL(T) is the Ginzburg-Landau coherence length). The magnetoconductivity is evaluated in the nonlocal fluctuation regime thereby
extending the existing theory valid in the local limit. We show that the Maki-Thompson (MT) and density-of-states (DOS) contributions
strongly compensate each other and their sum is negligible in comparison with the Aslamazov-Larkin (AL) term. The hierarchy
of the fluctuation contributions to the magnetoconductivity in the high-field limit is also qualitatively discussed.
Received 10 July 2002 / Received in final form 21 November 2002 Published online 7 May 2003 相似文献
12.
I.M. Sokolov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):369-373
We consider two-particle dispersion in a velocity field, where the relative two-point velocity scales according to v
2(r) ∝r
α and the corresponding correlation time scales as τ(r) ∝r
β, and fix α = 2/3, as typical for turbulent flows. We show that two generic types of dispersion behavior arize: For α/2 +
β < 1 the correlations in relative velocities decouple and the diffusion approximation holds. In the opposite case, α/2 +
β > 1, the relative motion is strongly correlated. The case of Kolmogorov flows corresponds to a marginal, nongeneric situation.
In this case, depending on the particular parameters of the flow, the dispersion behavior can be rather diffusive or rather
ballistic.
Received 13 March 2001 相似文献
13.
Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites
A. Weiße H. Fehske 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):487-494
We derive a realistic microscopic model for doped colossal magnetoresistance manganites, which includes the dynamics of charge,
spin, orbital and lattice degrees of freedom on a quantum mechanical level. The model respects the SU(2) spin symmetry and the full multiplet structure of the manganese ions within the cubic lattice. Concentrating on the hole
doped domain ( 0≤x≤0.5) we study the influence of the electron-lattice interaction on spin and orbital correlations by means of exact diagonalisation
techniques. We find that the lattice can cause a considerable suppression of the coupling between spin and orbital degrees
of freedom and show how changes in the magnetic correlations are reflected in dynamic phonon correlations. In addition, our
calculation gives detailed insights into orbital correlations and demonstrates the possibility of complex orbital states.
Received 4 September 2002 / Received in final form 8 November 2002 Published online 31 December 2002 相似文献
14.
N. Olivi-Tran N. Fraysse P. Girard M. Ramonda D. Chatain 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):217-222
We have performed noise measurements on suspended ropes of single wall carbon nanotubes (SWNT) between 1 and 300 K for different
values of dc current through the ropes. We find that the shot noise is suppressed by more than a factor 100 compared to the
full shot noise 2eI. We have also measured an individual SWNT and found a level of noise which is smaller than the minimum expected. Another
finding is the very low level of 1/f noise, which is significantly lower than previous observations. We propose two possible interpretations for the strong shot
noise reduction: i) Transport within a rope takes place through few nearly ballistic tubes within a rope and possibly involves
non integer effective charges with e
*∼ 0.3e. ii) A substantial fraction of the tubes conduct with a strong reduction of effective charge (by more than a factor 50).
Received 25 January 2002 Published online 19 July 2002 相似文献
15.
E. Cappelluti C. Grimaldi L. Pietronero 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):511-517
In small Fermi energy metals, disorder can deeply modify superconducting state properties leading to a strong suppression
of the critical temperature Tc. In this paper, we show that also normal state properties can be seriously influenced by disorder when the Fermi energy E
F is sufficiently small. We calculate the normal state spin susceptibility χ for a narrow band electron-phonon coupled metal
as a function of the non-magnetic impurity scattering rate . We find that as soon as is comparable to E
F, χ is strongly reduced with respect to its value in the clean limit. The effects of the electron-phonon interaction including
the nonadiabatic corrections are discussed. Our results strongly suggest that the recent finding on irradiated MgB2 samples can be naturally explained in terms of small E
F values associated with the σ-bands of the boron plane, sustaining therefore the hypothesis that MgB2 is a nonadiabatic metal.
Received 31 July 2002 / Received in final form 21 September 2002 Published online 31 December 2002 相似文献
16.
J.P. Salas M. I narrea A.I. Pascual 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):45-54
In the frame work of classical mechanics, we study the nonlinear dynamics of a single ion trapped in a Penning trap perturbed
by an electrostatic sextupolar perturbation. The perturbation is caused by a deformation in the configuration of the electrodes.
By using a Hamiltonian formulation, we obtain that the system is governed by three parameters: the z-component of the canonical angular momentum P
φ - which is a constant of the motion because the perturbation we assume is axial-symmetric -, the parameter δ that determines
the ratio between the axial and the cyclotron frequencies, and the parameter a which indicates how far from the ideal design the electrodes are. We study the case P
φ = 0. By means of surfaces of section, we show that the phase space structure is made of three fundamental families of orbits:
arch, loop and box orbits. The coexistence of these kinds of orbits depends on the parameter δ. The escape is also explained on the basis of
the shape of the potential energy surface as well as of the phase space structure.
Received 6 September 2001 / Received in final form 19 March 2002 Published online 28 June 2002 相似文献
17.
Y.Y. Goldschmidt Y. Shiferaw 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):87-95
In this paper we investigate the problem of a long self-avoiding polymer chain immersed in a random medium. We find that in
the limit of a very long chain and when the self-avoiding interaction is weak, the conformation of the chain consists of many
“blobs” with connecting segments. The blobs are sections of the molecule curled up in regions of low potential in the case
of a Gaussian distributed random potential or in regions of relatively low density of obstacles in the case of randomly distributed
hard obstacles. We find that as the strength of the self-avoiding interaction is increased the chain undergoes a delocalization
transition in the sense that the appropriate free energy per monomer is no longer negative. The chain is then no longer bound
to a particular location in the medium but can easily wander around under the influence of a small perturbation. For a localized
chain we estimate quantitatively the expected number of monomers in the “blobs” and in the connecting segments.
Received 13 November 2002 Published online 14 March 2003 相似文献
18.
S.G. Sharapov V.P. Gusynin H. Beck 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):45-51
We investigate a collective excitation (Leggett's mode) corresponding to small fluctuations of the relative phase of two condensates
in two-band superconductor using the effective “phase only” action. We consider the possibility of observing Leggett's mode
in MgB2 superconductor and conclude that for the known at present values of the two-band model parameters for MgB2 Leggett's mode arises above the two-particle threshold.
Received 10 May 2002 Published online 19 November 2002 相似文献
19.
Slow dynamics of density fluctuations near the colloidal glass transition is discussed from a new viewpoint by numerically
solving a nonlinear stochastic diffusion equation for the density fluctuations recently proposed by one of the present authors
(MT). The effects of spatial heterogeneities on the dynamics of density fluctuations are then investigated in an equilibrium
system. The spatial heterogeneities are generated by the nonlinear density fluctuations, while in a nonequilibrium system
they are described by a nonlinear deterministic equation for the average number density. The dynamics of equilibrium density
fluctuations is thus shown to be quite different from that of nonequilibrium ones, leading to a logarithmic decay followed
by less distinct α- and β-relaxation processes.
Received 9 March 2002 and Received in final form 19 September 2002 相似文献
20.
S. Zschocke O.P. Pavlenko B. Kämpfer 《The European Physical Journal A - Hadrons and Nuclei》2002,15(4):529-537
QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of mass parameters for the
lightest vector mesons ρ, ω and φ in a strongly interacting medium. For conditions relevant for the starting experiments at
HADES we find that the in-medium mass shifts of the ρ- and ω-mesons are governed, within the Borel QCD sum rule approach,
by the density and temperature dependence of the four-quark condensate. In particular, the variation of the strength of the
density dependence of the four-quark condensate reflects directly the decreasing mass of the ρ-meson and can lead to a change
of the sign of the ω-meson mass shift as a function of the density. In contrast, the in-medium mass of the φ-meson is directly
related to the chiral strange quark condensate which seems correspondingly accessible.
Received: 15 May 2002 / Accepted: 31 July 2002 / Published online: 10 December 2002
RID="a"
ID="a"e-mail: Kaempfer@fz.rossendorf.de
Communicated by A. Sch?fer 相似文献