共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Tsuchiizu P. Donohue Y. Suzumura T. Giamarchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):185-193
We investigate the physical properties of two coupled chains of electrons, with a nearly half-filled band, as a function of
the interchain hopping t
⊥ and the doping. We show that upon doping, the system undergoes a metal-insulator transition well described by a commensurate-incommensurate
transition. By using bosonization and renormalization we determine the full phase diagram of the system, and the physical
quantities such as the charge gap. In the commensurate phase two different regions, for which the interchain hopping is relevant
and irrelevant exist, leading to a confinement-deconfinement crossover in this phase. A minimum of the charge gap is observed
for values of t
⊥ close to this crossover. At large t
⊥ the region of the commensurate phase is enhanced, compared to a single chain. At the metal-insulator transition the Luttinger
parameter takes the universal value K
ρ
* = 1, in agreement with previous results on special limits of this model.
Received 31 July 2000 相似文献
2.
H. Fehske A.P. Kampf M. Sekania G. Wellein 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):11-16
In order to clarify the physics of the crossover from a Peierls band insulator to a correlated Mott-Hubbard insulator, we
analyze ground-state and spectral properties of the one-dimensional half-filled Holstein-Hubbard model using quasi-exact numerical
techniques. In the adiabatic limit the transition is connected to the band to Mott insulator transition of the ionic Hubbard
model. Depending on the strengths of the electron-phonon coupling and the Hubbard interaction the transition is either first
order or evolves continuously across a narrow intermediate phase with finite spin, charge, and optical excitation gaps.
Received 7 July 2002 / Received in final form 21 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: holger.fehske@physik.uni-greifswald.de 相似文献
3.
Y. Ōno R. Bulla A.C. Hewson 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):375-384
The Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized
dynamical mean-field theory recently developed by Bulla and Potthoff. The phase boundary of the metal-insulator transition
is obtained analytically as a function of the on-site Coulomb interaction at the d-orbital, the charge-transfer energy between the d- and p-orbitals and the hopping integrals between p-d, d-d and p-p orbitals. The result is in good agreement with the numerical results obtained from the exact diagonalization method.
Received 5 October 2000 and Received in final form 8 December 2000 相似文献
4.
W. Selke M. Pleimling D. Catrein 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):321-327
The axial next-nearest-neighbour Ising (ANNNI) model of finite thickness is studied. Using mean-field theory, Monte Carlo
simulations, and low-temperature analyses, phase diagrams are determined, with a distinct phase diagram for each film thickness.
The robustness of the phase diagrams against varying the couplings in the surface layers is analysed.
Received 19 March 2002 and Received in final form 2 April 2002 Published online 6 June 2002 相似文献
5.
A.A. Zvyagin A. Klümper J. Zittartz 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):25-36
The exactly solvable model of supersymmetric t - J chains (STJC) of correlated electrons with next-nearest-neighbour (NNN) interactions is proposed and studied. The model with
interactions between nearest neighbours and NNN interactions in one chain can also be considered as a two-chain model with
zigzag-like coupling between the chains. The NNN interaction (coupling between chains) causes the onset of additional Dirac
seas for low-lying charge and/or spin excitations. These Dirac seas change the low-energy (conformal) behavior of the model.
The filling of those seas depends on the values of the NNN coupling (interactions between chains), external magnetic field
and applied voltage. We identify the new ground state phases which appear due to the NNN as incommensurate ones. The NNN coupling
in the incommensurate phases induces spontaneous magnetization and/or spontaneous filling of the Dirac sea for charge excitations
(“spontaneous charge ordering”). The onset of this order implies a first order quantum phase transition driven by the field
with hysteresis phenomena.
Received 13 September 2000 相似文献
6.
G.I. Japaridze S. Sarkar 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):139-144
A one-dimensional model of interacting electrons with on-site U, nearest-neighbor V, and pair-hopping interaction W is studied at half-filling using the continuum limit field theory approach. The ground state phase diagram is obtained for
a wide range of coupling constants. In addition to the insulating spin-density wave (SDW) and charge-density wave (CDW) phases
for large U and V, respectively, we identify a bond-charge-density-wave (BCDW) phase W < 0, | U - 2V| < | 2W| and a bond-spin-density-wave (BSDW) for W > 0, | U - 2V| < W. The possibility of bond-located ordering results from the site-off-diagonal nature of the pair-hopping term and is a special
feature of the half-filled band case. The BCDW phase corresponding to an enhanced Peierls instability in the system. The BdSDW
is an unconventional insulating magnetic phase, characterized by a gapless spin excitation spectrum and a staggered magnetization
located on bonds between sites. The general ground state phase diagram including insulating, metallic, and superconducting
phases is discussed. A transition to the η-superconducting phase at | U - 2V| ≪ 2t?W is briefly discussed.
Received 20 February 2002 / Received in final form 11 April 2002 Published online 19 July 2002 相似文献
7.
B. Binz D. Baeriswyl B. Douçot 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(1):69-87
The weak coupling instabilities of a two dimensional Fermi system are investigated for the case of a square lattice using
a Wilson renormalization group scheme to one loop order. We focus on a situation where the Fermi surface passes through two
saddle points of the single particle dispersion. In the case of perfect nesting, the dominant instability is a spin density
wave but d-wave superconductivity as well as charge or spin flux phases are also obtained in certain regions in the space of coupling
parameters. The low energy regime in the vicinity of these instabilities can be studied analytically. Although saddle points
play a major role (through their large contribution to the single particle density of states), the presence of low energy
excitations along the Fermi surface rather than at isolated points is crucial and leads to an asymptotic decoupling of the
various instabilities. This suggests a more mean-field like picture of these instabilities, than the one recently established
by numerical studies using discretized Fermi surfaces.
Received 11 April 2001 and Received in final form 6 September 2001 相似文献
8.
V. Dureuil C. Ricolleau M. Gandais C. Grigis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):83-88
The crystalline structure of Co clusters embedded in an amorphous Al2O3 matrix was studied by transmission electron microscopy (TEM) and electron diffraction (TED). In the first stage of the growth
a metastable structure (body-centred-cubic) is observed. A face-centred-cubic phase (fcc) is found when the size of the clusters
increases ( diameter > 4 nm). The hexagonal-close-packed phase arises in the fcc phase by a succession of stacking faults at the largest sizes.
The mechanisms of phase transformation have been determined by using high resolution electron microscopy (HREM). The chemical
nature of the clusters, in particular the existence of Co-O bonds, was investigated by using electron energy loss spectroscopy
(EELS).
Received 03 July 2000 and Received in final form 22 December 2000 相似文献
9.
A. Pundt M. Dornheim M. Guerdane H. Teichler H. Ehrenberg M.T. Reetz N.M. Jisrawi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):333-337
An in situ synchrotron radiation study of quasi-free five nanometer-sized palladium clusters during hydrogen absorption is combined
with molecular dynamics simulations to investigate the structural development. In the diffraction patterns, strong intensity
changes are found that provide evidence for a structural phase transformation that is significantly different from the α--Pd-H bulk phase transition. The structural transition is reversible and driven by the hydrogen concentration. The intensity
changes are consistent with a cubic-to-icosahedral structural phase transition obtained in molecular dynamical simulations
using embedded-atom-method potentials.
Received 15 October 2001 and Received in final form 7 February 2002 相似文献
10.
T.A. Gloor M.E. Zhitomirsky T.M. Rice 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(4):491-497
We investigate multiexciton bound states in a semiconducting phase of divalent hexaborides. Due to three degenerate valleys
in both the conduction and valence bands the binding energy of a 6-exciton molecule is greatly enhanced by the shell effect.
The ground state energies of multiexciton molecules are calculated using the density functional formalism. We also show that
charged impurities stabilize multiexciton complexes leading to condensation of localized excitons. These complexes can act
as nucleation centers of local moments.
Received 24 October 2000 相似文献
11.
R. Citro M. Marinaro 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):55-60
Within a strong-coupling perturbative approach, based on a Cumulant Expansion of the extended single-band Hubbard model, we
show that the on-shell inverse scattering time deviates from the normal Fermi-liquid behavior near the points of the Fermi
surface connected by the characteristic wave-vector of an incommensurate charge density wave. The violation of the Fermi liquid
behavior is associated with a square root behavior of the inverse quasiparticle lifetime in proximity of a stripe phase. Some
relevant features observed in ARPES experiments on Bi2212 are qualitatively reproduced.
Received 28 February 2002 / Received in final form 7 May 2002 Published online 9 July 2002 相似文献
12.
A. Michel V. Pierron-Bohnes J.P. Jay P. Panissod S. Lefebvre M. Bessière H.E. Fischer G. Van Tendeloo 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):225-239
Epitaxial Co/Mn multilayers (0.75 to 6 nm Co, 0.4 nm Mn layer thickness) have been grown on mica substrates covered by a (0002)
Ru buffer layer. The structural properties of these layers have been studied using X-ray diffraction, nuclear magnetic resonance
(NMR), and high resolution transmission electron microscopy (HRTEM). The Co layers, grown as face centred cubic (fcc), were
found to be stabilised by the very thin Mn layers. Data obtained using X-ray diffraction and NMR were analysed and found to
be in good agreement, while Monte-Carlo simulations were used to interpret the data and calculate the expected diffracted
intensity and NMR spectra. The HRTEM data show that the Mn layers give rise to a large strain contrast extending, in the growth
direction, over a distance which exceeds the thickness of the Mn layers. The superlattices could be described as having an
fcc structure containing randomly located stacking faults with varying densities. The results verify the presence of a dominant,
almost perfect phase of fcc stacking, and of a faulted hcp phase, while the number of defects increases with the Co layer
thickness.
Received 27 October 1999 and Received in final form 29 May 2000 相似文献
13.
M. Modarres H.R. Moshfegh A. Sepahvand 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(2):159-166
The free energy of the homogeneous electron fluid at finite temperature is obtained using the lowest order constrained variational
(LOCV) method. In order to test the convergence of cluster expansion series the three-body cluster terms are calculated with
the LOCV correlation functions. The results agree reasonably with those of Monte Carlo, coupled-cluster, perturbational expansion
etc, techniques at zero temperature. The flashing and critical temperatures as well as the critical exponent are found to
be about 0.6, 1.3 eV and 0.384 respectively. A similar liquid-gas phase transition to that of nuclear matter and liquid He3 is observed.
Received 15 April 2002 / Received in final form 19 October 2002 Published online 4 February 2003
RID="a"
ID="a"e-mail: modarres@khayam.ut.ac.ir 相似文献
14.
S. Hémon A. Berthelot Ch. Dufour F. Gourbilleau E. Dooryhée S. Bégin-Colin E. Paumier 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):517-523
The irradiation effects induced by swift heavy ions are now widely described in `bulk' materials. It is shown here that the
behaviour of matter under irradiation depends on its crystalline state in the sense that a given material is all the more
sensitive to swift heavy ion irradiations as the mean crystallite size L is small. The present paper relates the experimental results obtained in yttrium oxide from `in situ' X-ray diffraction measurements. Three kinds of sample have been irradiated: sintered samples (L = 1μm), non-ground powders (L = 45 nm) and ground powders (L = 28 nm). A cubic to monoclinic phase transformation appears if the electronic energy loss of the incident particle is higher
than a threshold. The comparison between the different kinds of samples reveals that this phase transformation is all the
easier as the mean crystallite size of the target is weak.
Received 27 January 2000 and Received in final form 13 December 2000 相似文献
15.
Y. Mao T.C.B. McLeish P.I.C. Teixeira D.J. Read 《The European physical journal. E, Soft matter》2001,6(1):69-77
We address the effect of an asymmetric concentration-dependent mobility on the early stages of spinodal decomposition in polymer
blends and solutions, and characterise it quantitatively. This is particularly important when one of the components has a
slower dynamics than the other, e.g., because it is closer to its glass transition, or is weakly cross-linked. Composition mode coupling is proposed as the underlying
physical mechanism, and then investigated by means of numerical simulations of the Cahn-Hilliard equation in one (1d) and
two (2d) dimensions. In general, this coupling broadens the peak in the structure factor: in 1d an asymmetric concentration
profile is obtained, with sharpened interfaces, whereas in 2d the formation is favoured of sharp peaks of the phase rich in
the more mobile component. It is shown how the changing morphology of this phase-separating system can be described with the
aid of Minkowski functionals.
Received 28 August 2000 and Received in final form 18 July 2001 相似文献
16.
F.S. Csajka R.R. Netz C. Seidel J.-F. Joanny 《The European physical journal. E, Soft matter》2001,4(4):505-513
We investigate polyelectrolyte brushes using both scaling arguments and molecular dynamics simulations. As a main result,
we find a novel collapsed brush phase. In this phase, the height of the brush results from a competition between steric repulsion
between ions and monomers and an attractive force due to electrostatic correlations. As a result, the monomer density inside
the brush is independent of the grafting density and the polymerization index. For small ionic and monomer radii (or for large
Bjerrum length) the brush undergoes a first-order phase transition from the osmotic into the collapsed state.
Received 26 September 2000 相似文献
17.
Z. Gulácsi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):295-301
We report for the first time exact ground-states deduced for the D
= 2 dimensional generic periodic Anderson model at finite U, the Hamiltonian of the model not containing direct hopping terms for f-electrons (
t
f
= 0). The deduced itinerant phase presents non-Fermi liquid properties in the normal phase, emerges for real hybridization matrix
elements, and not requires anisotropic unit cell. In order to deduce these results, the plaquette operator procedure has been
generalised to a block operator technique which uses blocks higher than an unit cell and contains f-operator contributions acting only on a single central site of the block.
Received 1st July 2002 / Received in final form 16 September 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: gulacsi@heavy-ion.atomki.hu 相似文献
18.
G. Strobl 《The European physical journal. E, Soft matter》2000,3(2):165-183
Based on broad and detailed evidence from a large variety of experiments on several polymer systems carried out by other authors
and ourselves, a novel concept for understanding the crystallization of polymers from the melt is developed. The experiments
generally indicate that the formation and growth of the lamellar crystallites is a multi-step process passing over intermediate
states. We suggest a specific route which is compatible with the observations. It is proposed that the initial step is always
the creation of a mesomorphic layer which spontaneously thickens, up to a critical value, where it solidifies through a cooperative
structural transition. The transition produces a granular crystalline layer, which transforms in the last step into homogeneous
lamellar crystallites. The model leads to predictions about the temperature dependencies of the crystal thickness and the
growth rate which are at variance with conventional views but in agreement with findings in recent experiments.
Received 17 February 2000 and Received in final form 30 March 2000 相似文献
19.
V.V. Savkin A.N. Rubtsov T. Janssen 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):525-531
The classical two-dimensional discrete frustrated φ
4
model is studied by Monte Carlo simulations. The correlation function is obtained for two values of a parameter d that determines the frustration in the model. The ground state is a ferro-phase for d
= - 0.35 and a commensurate phase with period N
= 6 for d
= - 0.45. Mean field predicts that at higher temperature the system enters a para-phase via an incommensurate state, in both cases. Monte Carlo data for d
= - 0.45 show two phase transitions with a floating-incommensurate phase between them. The phase transition at higher temperature
is of the Kosterlitz-Thouless type. Analysis of the data for d
= - 0.35 shows only a single phase transition between the floating-fluid phase and the ferro-phase within the numerical error.
Received 16 December 2002 / Received in final form 17 January 2003 Published online 6 March 2003
RID="a"
ID="a"e-mail: vladimir@shg.ru 相似文献
20.
V.P. Zhdanov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):97-100
We present Monte Carlo simulations of the ripening of 2D islands in the case when the formation of the monomer-monomer bonds
is kinetically limited. The results obtained indicate that such limitations may modify the early stage of the kinetics. Asymptotically,
the ripening is described by the Lifshitz-Slyozov law.
Received 29 August 2000 相似文献