共查询到20条相似文献,搜索用时 31 毫秒
1.
R. Zitzler Th. Pruschke R. Bulla 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):473-481
We discuss the ground state magnetic phase diagram of the Hubbard model off half filling within the dynamical mean-field theory.
The effective single-impurity Anderson model is solved by Wilson's numerical renormalization group calculations, adapted to
symmetry broken phases. We find a phase separated, antiferromagnetic state up to a critical doping for small and intermediate
values of U, but could not stabilize a Néel state for large U and finite doping. At very large U, the phase diagram exhibits an island with a ferromagnetic ground state. Spectral properties in the ordered phases are discussed.
Received 9 January 2002 Published online 25 June 2002 相似文献
2.
3.
J. Wang K.-Q. Xia 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,37(1):127-136
We have studied the dynamics of the contact line of a viscous liquid on a solid substrate with macroscopic random defects. We have first characterized the friction force f0 at microscopic scale for a substrate without defects; f0 is found to be a strongly nonlinear function of the velocity U of the contact line. In presence of macroscopic defects, we find that the applied force F(U) is simply shifted with respect to f0(U) by a constant: we do not observe any critical behavior at the depinning transition. The only observable effect of the substrate disorder is to increase the hysteresis. We have also performed realistic numerical simulation of the motion of the contact line. Using the same values of the parameters as in the experiment, we find that the experimental data is qualitatively well reproduced. In light of experimental and numerical results, we discuss the possibility of measuring a true critical behavior.Received: 6 October 2003, Published online: 19 February 2004PACS:
46.65. + g Random phenomena and media - 64.60.Ht Dynamic critical phenomena - 68.08.Bc Wetting 相似文献
4.
M.L. Ndawana R.A. Römer M. Schreiber 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):399-407
We compute the number level variance Σ
2 and the level compressibility χ from high precision data for the Anderson model of localization and show that they can be
used in order to estimate the critical properties at the metal-insulator transition by means of finite-size scaling. With
N, W, and L denoting, respectively, linear system size, disorder strength, and the average number of levels in units of the mean level
spacing, we find that both χ(N, W) and the integrated Σ
2 obey finite-size scaling. The high precision data was obtained for an anisotropic three-dimensional Anderson model with disorder
given by a box distribution of width W/2. We compute the critical exponent as ν≈ 1.45±0.12 and the critical disorder as W
c≈ 8.59±0.05 in agreement with previous transfer-matrix studies in the anisotropic model. Furthermore, we find χ≈ 0.28±0.06
at the metal-insulator transition in very close agreement with previous results.
Received 1st November 2001 and Received in final form 8 March 2002 Published online 6 June 2002 相似文献
5.
S. Hébert A. Maignan R. Frésard M. Hervieu R. Retoux C. Martin B. Raveau 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):85-89
The doping of the manganese site by iridium (up to 15%) in the small A cation manganites Pr1-xCaxMnO3 ( 0.4 ?
x
? 0.8), has been investigated as a new method to suppress charge-ordering and induce CMR effects. Ir doping leads to ferromagnetism
and to insulator to metal transitions, with high transition temperatures reaching 180 K and CMR ratio in 7 T as large as 104. The efficiency with which iridium induces ferromagnetism and CMR is compared to previous results obtained with other substitutions
(Ru, Rh, Ni, Cr...). The ionic radius of the foreign cations and their mixed-valencies are found to be the main parameters
governing the ability to collapse the charge-ordered state.
Received 14 May 2001 and Received in final form 2 July 2001 相似文献
6.
R. Citro M. Marinaro 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(3):343-348
Within the single band 2D-Hubbard model treated by means of a strong-coupling approach based on a cumulant expansion and a
nonstandard diagrammatic technique, we discuss the existence of critical charge fluctuations that could give rise to an instability
towards a phase separation (PS). It turns out that such instability exists and evolves into an incommensurate charge density
wave (ICDW) when long-range Coulomb forces are taken into account. We find a stripe phase with a crossover from diagonal to
vertical stripes at increasing doping in the range 0.01 ?δ? 0.2 and increasing Coulomb potential U, similarly to recent NMR experiments on La
2 - x
Sr
x
CuO
4.
Received 20 November 2000 相似文献
7.
Enhanced electron screening in d (d, p)t for deuterated Ta* 总被引:1,自引:0,他引:1
F. Raiola P. Migliardi G. Gyürky M. Aliotta A. Formicola R. Bonetti C. Broggini L. Campajola P. Corvisiero H. Costantini J. Cruz A. D'Onofrio Z. Fülöp G. Gervino L. Gialanella A. Guglielmetti G. Imbriani C. Gustavino A.P. Jesus M. Junker R.W. Kavanagh P.G.P. Moroni A. Ordine J.V. Pinto P. Prati V. Roca J.P. Ribeiro D. Rogalla C. Rolfs M. Romano F. Schümann D. Schürmann E. Somorjai F. Strieder F. Terrasi H.P. Trautvetter S. Zavatarelli 《The European Physical Journal A - Hadrons and Nuclei》2002,13(3):377-382
The recent observation of a large electron screening effect in the d(d, p)t reaction using a deuterated Ta target has been
confirmed using somewhat different experimental approaches: U
e = 309±12 eV for the electron screening potential energy. The high U
e value arises from the environment of the deuterons in the Ta matrix, but a quantitative explanation is missing.
Received: 21 December 2001 / Accepted: 29 January 2002 相似文献
8.
F. Selva J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(3):441-449
We study the difference between on site Hubbard and long range Coulomb repulsions for two interacting particles in a disordered
chain. The system size L (in units of the lattice spacing) is of the order of the one particle localization length and the energies are taken near
the band center. In the two cases, the limits of weak and strong interactions are characterized by uncorrelated energy levels
and are separated by a crossover regime where the states are more extended and the spectra more rigid. U denoting the interaction strength and t the kinetic energy scale, the crossovers take place for interaction energy to kinetic energy ratios U/t and U/(2tL) of order one, for Hubbard and Coulomb repulsions respectively. While Hubbard repulsion can only yield weak critical chaos
with intermediate spectral statistics, Coulomb repulsion can drive the two particle system to quantum chaos with Wigner-Dyson
spectral statistics. The interaction matrix elements are studied to explain this difference.
Received 21 March 2000 and Received in final form 5 February 2001 相似文献
9.
D. Dantchev J. Rudnick 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):251-268
We study the behavior of systems in which the interaction contains a long-range component that does not dominate the critical
behavior. Such a component is exemplified by the van der Waals force between molecules in a simple liquid-vapor system. In
the context of the mean spherical model with periodic boundary conditions we are able to identify, for temperatures close
above T
c, finite-size contributions due to the subleading term in the interaction that are dominant in this region decaying algebraically as a function of L. This mechanism goes beyond the standard formulation of the finite-size scaling but is to be expected in real physical systems.
We also discuss other ways in which critical point behavior is modified that are of relevance for analysis of Monte Carlo
simulations of such systems.
Received 21 November 2000 and Received in final form 28 February 2001 相似文献
10.
H. Iwasaki T. Motobayashi H. Akiyoshi Y. Ando N. Fukuda H. Fujiwara Zs. Fülöp K. I. Hahn Y. Higurashi M. Hirai I. Hisanaga N. Iwasa T. Kijima A. Mengoni T. Minemura T. Nakamura M. Notani S. Ozawa H. Sagawa H. Sakurai S. Shimoura S. Takeuchi T. Teranishi Y. Yanagisawa M. Ishihara 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):55-58
Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and
transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
11.
P. Estrela A. de Visser T. Naka F.R. de Boer L.C.J. Pereira 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):449-454
The effect of hydrostatic pressure ( p
? 1.8 GPa) on the non-Fermi liquid state of U2Pt2In is investigated by electrical resistivity measurements in the temperature interval 0.3-300 K. The experiments were carried
out on single-crystals with the current along (
I
||
c
) and perpendicular (
I
||
a
) to the tetragonal axis. The pressure effect is strongly current-direction dependent. For I
||
a we observe a rapid recovery of the Fermi-liquid T2-term with pressure. A comparison of the data with the magnetotransport theory of Rosch provides evidence for the location
of U2Pt2In at an antiferromagnetic quantum critical point. For I
||
c the resistivity increases under pressure, indicating the enhancement of an additional scattering mechanism.
Received 2 March 2001 and Received in final form 29 June 2001 相似文献
12.
Recent experiments have demonstrated that the dynamics in liquids close to the glass transition temperature is strongly heterogeneous.
The characteristic size of these heterogeneities has been measured to be a few nanometers at T
g. We extend here a recent model for describing the heterogeneous nature of the dynamics which allows both to derive this length
scale and the right orders of magnitude of the heterogeneities of the dynamics close to the glass transition. Our model allows
then to interpret quantitatively small probes diffusion experiments.
Received 29 March 2002 and Received in final form 11 November 2002
RID="a"
ID="a"e-mail: long@lps.u-psud.fr 相似文献
13.
H. Chamati 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):241-249
The finite-size critical properties of the (n) vector ϕ4 model, with long-range interaction decaying algebraically with the interparticle distance r like r
-d - σ, are investigated. The system is confined to a finite geometry subject to periodic boundary condition. Special attention
is paid to the finite-size correction to the bulk susceptibility above the critical temperature T
c. We show that this correction has a power-law nature in the case of pure long-range interaction i.e. 0 < σ < 2 and it turns out to be exponential in case of short-range interaction i.e.σ = 2. The results are valid for arbitrary dimension d, between the lower ( d
< = σ) and the upper ( d
> = 2σ) critical dimensions.
Received 2 July 2001 and Received in final form 4 Septembre 2001 相似文献
14.
Steven C. Pieper 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):75-79
Quantum Monte Carlo calculations using realistic two- and three-nucleon interactions are presented for nuclei with up to ten
nucleons. Our Green's function Monte Carlo calculations are accurate to ∼1-2% for the binding energy. We have constructed
Hamiltonians using the Argonne v18
NN interaction and reasonable three-nucleon interactions that reproduce the energies of these nuclear states with only ∼500
keV rms error. Other predictions, such as form factors, decay rates, and spectroscopic factors also agree well with data.
Some of these results are presented to show that ab initio calculations of light nuclei are now well in hand.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
15.
J. Lages D.L. Shepelyansky 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(1):129-133
We study analytically and numerically the problem of two particles with a long range attractive interaction on a two-dimensional
(2d) lattice with disorder. It is shown that below some critical disorder the interaction creates delocalized coupled states
near the Fermi level. These states appear inside well localized noninteracting phase and have a form of two-particle ring
which diffusively propagates over the lattice.
Received 29 September 2000 and Received in final form 15 January 2001 相似文献
16.
A. Urbina C. Díaz-Paniagua A.F. Braña F. Batallán 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):463-468
We present measurements of the diagonal Rxx and off-diagonal Rxy magnetoresistance under quantum Hall conditions on several high electron mobility transistors (HEMT) based on InxGa1-xAs quantum wells. From the magnetoresistance tensor we obtain the longitudinal conductivity σ
xx
. We study the transport mechanisms near the σ
xx
minima at temperatures ranging between 2 K and 35 K; activated transport is the dominant mechanism for temperatures above
7 K while variable range hopping conductivity is significant for lower temperatures. We show that electron-electron correlations
should be taken into account to explain the conductivity vs temperature behaviour below 5 K. Finally, we study the behaviour of the localization length as a function of Landau level
filling and obtain a critical exponent γ = 3.45±0.15.
Received 6 June 2001 and Received in final form 16 October 2001 相似文献
17.
A. Díaz-Sánchez A. Pérez-Garrido 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):483-486
The relaxation of the specific heat and the entropy to their equilibrium values is investigated numerically for the three-dimensional
Coulomb glass at very low temperatures. The long time relaxation follows a stretched exponential function, f (t) = f
0exp - (t/τ)β
, with the exponent β increasing with the temperature. The relaxation time diverges as an Arrhenius law when T→ 0.
Received 24 May 2001 and Received in final form 12 September 2001 相似文献
18.
D.V. Fisher Y. Maron 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):349-359
Accurate treatment of the plasma density effects requires a detailed knowledge of the spatial distribution of individual ions
around a test ion. In the present work, rigorous expressions are derived for the main 2- and 3-particle spatial distribution
functions involving the nearest neighbor (NN) and the next-nearest neighbor (NNN) ions. These expressions, valid for both
ideal and nonideal plasmas, present the distributions as functionals of the potentials U
NN and U
NNN at the nearest and next-nearest ion locations. All of the distribution functions except one are derived and discussed in
the present work for the first time ever. For utilization of our results in practical calculations, we suggest semi-empirical
expressions for U
NN and U
NNN in the ion-ion coupling parameter range 0 ?Γ < 1. In order to test the accuracy of our expressions for U
NN and U
NNN we conduct Molecular Dynamics (MD) simulations. The simulations utilize the pure Coulomb particle-particle interaction potentials,
regularized at close range to avoid classical Coulomb collapse, and are free from the assumptions made to find U
NN and U
NNN. Thus, the results of the MD simulations provide an independent test of our theoretical results. Excellent agreement has
been found between the results of the theory and of the MD simulations. Finally, we outline the implications of the present
findings on the problem of tunneling and charge exchange in dense plasmas.
Received 27 October 2000 and Received in final form 30 January 2001 相似文献
19.
R.-J. Tarento P. Joyes J. van de Walle M. Nakamura 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):111-114
We investigate the electron capture occurring in the collision between an ion A+ and a cluster An (n = 5). The process has been modelled within the Hubbard Hamiltonian,which takes into account the intrasite U electron correlation. An exact procedure has been numerically applied which involves all the excited states to examine the
time evolution of the system during the collision. We have applied the model to the sodium case. We have investigated the
time evolution of the electron population during the collision on the projectile versus the kinetic energy of the projectile. It displays some oscillations which means that the electron exchanges between the ion
and the cluster occurs alternatively in one direction and the other. We also vary U and examine its influence on the dynamics of the oscillation of the average population. Finally the cross section is derived
versus the energy and U.
Received 29 November 2000 相似文献
20.
We investigate η- mixing in infrared regularized U(3) chiral perturbation theory by calculating the η and masses up to one-loop order. From this analysis it becomes obvious that even at leading order η--mixing does not obey the usually assumed one-mixing-angle scheme if large N
c counting rules are not employed.
Received: 12 March 2001 / Accepted: 4 July 2001 相似文献