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1.
We present a detailed derivation of the Gutzwiller approximation for multi-band Hubbard models with density-density Coulomb
interactions. For the one-band Hubbard model we introduce a mathematically well-defined formalism which is easily generalized
to the multi-band case. In contrast to earlier attempts, our approach allows us to include inter-orbital hopping terms in
the Hamiltonian.
Received: 9 December 1997 / Revised and accepted: 6 March 1998 相似文献
2.
V. Meden W. Metzner U. Schollwöck O. Schneider T. Stauber K. Schönhammer 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):631-646
We present a study of the one-particle spectral properties for a variety of models of Luttinger liquids with open boundaries.
We first consider the Tomonaga-Luttinger model using bosonization. For weak interactions the boundary exponent of the power-law
suppression of the spectral weight close to the chemical potential is dominated by a term linear in the interaction. This
motivates us to study the spectral properties also within the Hartree-Fock approximation. It already gives power-law behavior
and qualitative agreement with the exact spectral function. For the lattice model of spinless fermions and the Hubbard model
we present numerically exact results obtained using the density-matrix renormalization-group algorithm. We show that many
aspects of the behavior of the spectral function close to the boundary can again be understood within the Hartree-Fock approximation.
For the repulsive Hubbard model with interaction U the spectral weight is enhanced in a large energy range around the chemical potential. At smaller energies a power-law suppression,
as predicted by bosonization, sets in. We present an analytical discussion of the crossover and show that for small U it occurs at energies exponentially (in -1/U) close to the chemical potential, i.e. that bosonization only holds on exponentially small energy scales. We show that such a crossover can also be found in other
models.
Received 8 February 2000 and Received in final form 25 April 2000 相似文献
3.
C. Honerkamp M. Salmhofer T.M. Rice 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(1):127-134
We extend the analysis of the renormalization group flow in the two-dimensional Hubbard model close to half-filling using
the recently developed temperature flow formalism. We investigate the interplay of d-density wave and Fermi surface deformation tendencies with those towards d-wave pairing and antiferromagnetism. For a ratio of next nearest to nearest neighbor hoppings, t'/t = - 0.25, and band fillings where the Fermi surface is inside the Umklapp surface, only the d-pairing susceptibility diverges at low temperatures. When the Fermi surface intersects the Umklapp surface close to the saddle
points, d-wave pairing, d-density wave, antiferromagnetic and, to a weaker extent, d-wave Fermi surface deformation susceptibilities grow together when the interactions flow to strong coupling. We interpret
these findings as indications for a non-trivial strongly coupled phase with short-ranged superconducting and antiferromagnetic
correlations, in close analogy with the spin liquid ground state in the well-understood two-leg Hubbard ladder.
Received 23 January 2002 相似文献
4.
S. Pairault D. Sénéchal A.-M.S. Tremblay 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(1):85-105
The strong-coupling perturbation theory of the Hubbard model is presented and carried out to order (t/U)5 for the one-particle Green function in arbitrary dimension. The spectral weight is expressed as a Jacobi continued fraction and compared with new Monte-Carlo data of the one-dimensional, half-filled Hubbard
model. Different regimes (insulator, conductor and short-range antiferromagnet) are identified in the temperature-hopping
integral (T,t) plane. This work completes a first paper on the subject (Phys. Rev. Lett. 80, 5389 (1998)) by providing details on diagrammatic rules and higher-order results. In addition, the non half-filled case,
infinite resummations of diagrams and the double occupancy are discussed. Various tests of the method are also presented.
Received 25 October 1999 相似文献
5.
V.Yu. Irkhin A.V. Zarubin 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):463-468
The Kondo divergences owing to interaction of current carriers with local moments in highly correlated electron systems are
considered within the Hubbard and s-d exchange models with infinitely strong on-site interaction, the many-electron Hubbard representation being used. The picture
of density of states containing a peak at the Fermi level is obtained. Various forms of the self-consistent approximation
are used. The problem of the violation of analytical properties of the Green's function is discussed. Smearing of the “Kondo”
peak owing to spin dynamics and finite temperatures is investigated.
Received 25 November 1999 and Received in final form 31 January 2000 相似文献
6.
M. Cini A. Balzarotti G. Stefanucci 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):269-280
We study the Cu5O4 cluster by exact diagonalization of a three-band Hubbard model and show that bound electron or hole pairs are obtained at
appropriate fillings, and produce superconducting flux quantization. The results extend earlier cluster studies and illustrate
a canonical transformation approach to pairing that we have developed recently for the full plane. The quasiparticles that
in the many-body problem behave like Cooper pairs are W
=0 pairs, that is, two-hole eigenstates of the Hubbard Hamiltonian with vanishing on-site repulsion. The cluster allows W
=0 pairs of d symmetry, due to a spin fluctuation, and ssymmetry, due to a charge fluctuation. Flux quantization is shown to be a manifestation of symmetry properties that hold for
clusters of arbitrary size.
Received 23 July 1999 相似文献
7.
R. Lacaze A. Morel B. Petersson J. Schröper 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):509-523
We present an investigation of the 2D attractive Hubbard model, considered as an effective model relevant to superconductivity
in strongly interacting electron systems. We use both hybrid Monte-Carlo simulations and existing hopping parameter expansions
to explore the low temperature domain. The increase of the static S-wave pair correlation with decreasing temperature, which depends weakly on the band filling in the explored temperature range,
is analyzed in terms of an expected Kosterlitz-Thouless superconducting transition. Using both our data and previously published
results, we show that the evidence for this transition is weak: If it exists, its temperature is very low. The number of unpaired
electrons remains nearly constant with temperature at fixed attractive potential strength. In contrast, the static magnetic
susceptibility decreases fast with temperature, and cannot be related only to pair formation. We introduce a method by which
the Padé approximants of the existing series for the susceptibility give sensible results down to rather low temperature region,
as shown by comparison with our numerical data.
Received: 30 October 1996 / Revised: 23 October 1997 / Accepted: 29 January 1998 相似文献
8.
D. Lee 《The European Physical Journal A - Hadrons and Nuclei》2008,35(2):171-187
The symmetric heavy-light ansatz is a method for finding the ground state of any dilute unpolarized system of attractive two-component
fermions. Operationally it can be viewed as a generalization of the Kohn-Sham equations in density functional theory applied
to N -body density correlations. While the original Hamiltonian has an exact Z2 symmetry, the heavy-light ansatz breaks this symmetry by skewing the mass ratio of the two components. In the limit where
one component is infinitely heavy, the many-body problem can be solved in terms of single-particle orbitals. The original
Z2 symmetry is recovered by enforcing Z2 symmetry as a constraint on N -body density correlations for the two components. For the 1D, 2D, and 3D attractive Hubbard models the method is in very
good agreement with exact Lanczos calculations for few-body systems at arbitrary coupling. For the 3D attractive Hubbard model
there is very good agreement with lattice Monte Carlo results for many-body systems in the limit of infinite scattering length. 相似文献
9.
W. Fettes I. Morgenstern 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):635-639
We perform numerical simulations of the Hubbard model using the projector Quantum Monte Carlo method. A novel approach for
finite size scaling is discussed. We obtain evidence in favor of d-wave superconductivity in the repulsive Hubbard model. For U=4, is roughly estimated as K.
Received 8 September 1998 相似文献
10.
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
11.
E. Perfetto G. Stefanucci M. Cini 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):139-142
We show that different non-conventional superconductors have one fundamental feature in common: pair eigenstates of the Hamiltonian
are repulsion-free, the W = 0 pairs. In extended Hubbard models, pairing can occur for reasonable parameter values. For (N, N) nanotubes the binding energy of the pair depends strongly on the filling and decreases towards a reduced but nonzero value
for the graphite sheet N → ∞.
Received 13 July 2002 Published online 29 November 2002 相似文献
12.
M. Brunner F.F. Assaad A. Muramatsu 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):209-212
We present a new finite-temperature quantum Monte Carlo algorithm to compute imaginary-time Green functions for a single hole
in the t-J model on non-frustrated lattices. Spectral functions are obtained with the Maximum Entropy method. Simulations of the one-dimensional
case show that a simple charge-spin separation Ansatz is able to describe the overall features of the spectral function such as the bandwidth and the compact support of the spectral function, over the whole energy range for values of J
/
t from 1/3 to 4. This is contrasted with the two-dimensional case. The quasiparticle weight Zk is computed on lattices up to L
=128 sites in one dimension, and scales as .
Received 15 February 2000 相似文献
13.
14.
D. Sa C. Gros 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):421-428
An effective intra- and inter-ladder charge-spin Hamiltonian for the quarter-filled ladder compound α'-NaV2O5 has been derived by using the standard canonical transformation method. In the derivation, it is clear that a finite inter-site
Coulomb repulsion is needed to get a meaningful result otherwise the perturbation becomes ill-defined. Various limiting cases
depending on the values of the model parameters have been analyzed in detail and the effective exchange couplings are estimated.
We find that the effective intra-ladder exchange may become ferromagnetic for the case of zig-zag charge ordering in a purely
electronic model. We estimate the magnitude of the effective inter-rung Coulomb repulsion in a ladder and find it to be about
one-order of magnitude too small in order to stabilize charge-ordering.
Received 24 March 2000 and Received in final form 30 August 2000 相似文献
15.
A. Avella F. Mancini D. Villani H. Matsumoto 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(3):303-311
The addition to the Hubbard Hamiltonian of a t' diagonal hopping term, which is considered to be material dependent for high-T
c cuprate superconductors, is generally suggested to obtain a model capable to describe the physics of high-T
c cuprate materials. In this line of thinking, the two-dimensional t-t'-U model has been studied by means of the Composite Operator Method, which allows to determine the dynamics in a fully self-consistent
way by use of symmetry requirements, as the ones coming from the Pauli principle. At first, some local quantities have been
calculated to be compared with quantum Monte Carlo data. Then, the structure of the energy bands, the shape of the Fermi surface
and the position of the van Hove singularity have been computed as functions of the model parameters and studied by the light
of the available experimental data. The results of our study show that there exists two sets of parameters that allows the
model to describe the relevant features of the 1-layer compounds Nd2-xCexCuO4 and La2-xSrxCuO4. On the other hand, for the 2-layer compound YBa2Cu3O 7 - δ is not possible to find a reasonable set of parameters which could reproduce the position of the van Hove singularity as
predicted by ARPES experiments. Hence, it results questionable the existence of an unique model that could properly describe
the variety of cuprate superconductors, as the two-dimensional t-t'-U model was thought to be.
Received 29 March 2000 and Received in final form 10 August 2000 相似文献
16.
We consider a modified version of the one-dimensional Hubbard model, the t
1
-
t
2
Hubbard chain, which includes an additional next-nearest-neighbor hopping. It has been shown that at weak coupling this model
has a Luttinger liquid phase or a spin liquid phase depending upon the ratio of t2 to t1. Additionally if the on-site interaction U is large enough, the ground state is fully polarized. Using exact diagonalization and the density-matrix renormalization
group, we show that the transition to the ferromagnetic phase is either of first or second order depending on whether the
Luttinger liquid or spin liquid is being destabilized. Since we work at T
=0, the second order transition is a quantum magnetic critical point.
Received 21 July 1999 相似文献
17.
Ph. Brune A.P. Kampf 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):241-245
We apply a diagrammatic expansion method around the atomic limit () for the U-t-t
' Hubbard model at half filling and finite temperature by means of a continued fraction representation of the one-particle
Green's function. From the analysis of the spectral function we find an energy dispersion relation with a modulation of the energy gap in the insulating phase. This anisotropy is compared with experimental ARPES results on insulating
cuprates.
Received 18 May 2000 and Received in final form 9 August 2000 相似文献
18.
M. Potthoff W. Nolting 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):555-568
The correlation-driven transition from a paramagnetic metal to a paramagnetic Mott-Hubbard insulator is studied within the
half-filled Hubbard model for a thin-film geometry. We consider simple-cubic films with different low-index surfaces and film
thickness d ranging from d=1 (two-dimensional) up to d=8. Using the dynamical mean-field theory, the lattice (film) problem is self-consistently mapped onto a set of d single-impurity Anderson models which are indirectly coupled via the respective baths of conduction electrons. The impurity models are solved at zero temperature using the exact-diagonalization
algorithm. We investigate the layer and thickness dependence of the electronic structure in the low-energy regime. Effects
due to the finite film thickness are found to be the more pronounced the lower is the film-surface coordination number. For
the comparatively open sc(111) geometry we find a strong layer dependence of the quasi-particle weight while it is much less
pronounced for the sc(110) and the sc(100) film geometries. For a given geometry and thickness d there is a unique critical interaction strength U
c2
(d) at which all effective masses diverge and there is a unique strength U
c1
(d) where the insulating solution disappears. U
c2
(d) and U
c1
(d) gradually increase with increasing thickness eventually approaching their bulk values. A simple analytical argument explains
the complete geometry and thickness dependence of Uc2. Uc1 is found to scale linearly with Uc2.
Received 19 August 1998 相似文献
19.
E. Orignac Y. Suzumura 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(1):57-67
We study the interplay of Anderson localization and interaction in a two chain Hubbard ladder allowing for arbitrary ratio
of disorder strength to interchain coupling. We obtain three different types of spin gapped localized phases depending on
the strength of disorder: a pinned 4k
F Charge Density Wave (CDW) for weak disorder, a pinned 2k
F CDWπ for intermediate disorder and two independently pinned single chain 2k
F CDW for strong disorder. Confinement of electrons can be obtained as a result of strong disorder or strong attraction. We
give the full phase diagram as a function of disorder, interaction strength and interchain hopping. We also study the influence
of interchain hopping on localization length and show that localization is enhanced by a small interchain hopping but suppressed
by a large interchain hopping.
Received 6 April 2001 相似文献
20.
Th. Maier M. Jarrell Th. Pruschke J. Keller 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):613-624
We develop a Non-Crossing Approximation (NCA) for the effective cluster problem of the recently developed Dynamical Cluster
Approximation (DCA). The DCA technique includes short-ranged correlations by mapping the lattice problem onto a self-consistently
embedded periodic cluster of size . It is a fully causal and systematic approximation to the full lattice problem, with corrections in two dimensions. The NCA we develop is a systematic approximation with corrections . The method will be discussed in detail and results for the one-particle properties of the Hubbard model are shown. Near
half filling, the spectra display pronounced features including a pseudogap and non-Fermi-liquid behavior due to short-ranged
antiferromagnetic correlations.
Received 16 June 1999 相似文献