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1.
R. Bulla M. Potthoff 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):257-264
The Mott-Hubbard metal-insulator transition is studied within a simplified version of the Dynamical Mean-Field Theory (DMFT)
in which the coupling between the impurity level and the conduction band is approximated by a single pole at the Fermi energy.
In this approach, the DMFT equations are linearized, and the value for the critical Coulomb repulsion can be calculated analytically. For the symmetric single-band Hubbard model at zero temperature, the critical value is found
to be given by 6 times the square root of the second moment of the free (U=0) density of states. This result is in good agreement with the numerical value obtained from the Projective Selfconsistent
Method and recent Numerical Renormalization Group calculations for the Bethe and the hypercubic lattice in infinite dimensions.
The generalization to more complicated lattices is discussed. The “linearized DMFT” yields plausible results for the complete
geometry dependence of the critical interaction.
Received 6 May 1999 and Received in final form 2 July 1999 相似文献
2.
F.F. Assaad M. Imada 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):595-598
The dispersion relation of a doped hole in the half-filled 2D Hubbard model is shown to follow a law around the and points in the Brillouin zone. Upon addition of pair-hopping processes this dispersion relation is unstable towards a law. The above follows from T=0 Quantum Monte-Carlo calculations of the single particle spectral function on lattices. We discuss finite dopings and argue that the added term restores coherence to charge dynamics and drives the system
towards a d
x2 - y2
superconductor.
Received 22 March 1999 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.
J. Bauer A. C. Hewson 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):235-249
We analyze the properties of the quasiparticle excitations of metallic
antiferromagnetic states in a strongly correlated electron system. The study is based on
dynamical mean field theory (DMFT) for the infinite dimensional Hubbard model with
antiferromagnetic symmetry breaking. Self-consistent solutions of the DMFT
equations are calculated using the numerical renormalization group (NRG). The
low energy behavior in these results is then analyzed in terms
of renormalized quasiparticles. The parameters for these quasiparticles are
calculated directly from the NRG derived self-energy, and also from the low
energy fixed point of the effective impurity model. From these the quasiparticle
weight and the effective mass are deduced. We show that
the main low energy features of the k-resolved spectral density can be understood in
terms of the quasiparticle picture. We also find that Luttinger's theorem
is satisfied for the total electron number in the doped antiferromagnetic
state. 相似文献
5.
S. Ejima F. Gebhard R. M. Noack 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):191-200
We use the Random Dispersion Approximation (RDA) to study the
Mott-Hubbard transition in the Hubbard model at half band filling.
The RDA becomes exact for the Hubbard model in infinite dimensions.
We implement the RDA on finite chains and employ the Lanczos exact
diagonalization method in real space to calculate the ground-state energy,
the average double occupancy, the charge gap, the momentum distribution,
and the quasi-particle weight. We find a satisfactory agreement with
perturbative results in the weak- and strong-coupling limits.
A straightforward extrapolation of the RDA data
for L ≤ 14 lattice results in a continuous Mott-Hubbard transition at
Uc≈W.
We discuss the significance of a possible signature
of a coexistence region between insulating and metallic
ground states in the RDA that would correspond to
the scenario of a discontinuous Mott-Hubbard transition
as found in numerical investigations
of the Dynamical Mean-Field Theory for the Hubbard model. 相似文献
6.
J. Kurzyk W. Wójcik J. Spałek 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):385-398
The method used earlier for analysis of correlated nanoscopic systems is extended to infinite (periodic) s-band-like systems
described by the Hubbard model. The optimized single-particle Wannier wave functions contained in the parameters of the extended
Hubbard model (in the nearest-neghbor hopping (-t), in the magnitude of the intraatomic interaction U, and in other parameters) are determined explicitly in the correlated state for the electronic systems of various symmetries
and dimensions: Hubbard chain, square and triangular planar lattices, and the three cubic lattices (SC, BCC, FCC). In effect,
the evolution of the electronic properties as a function of interatomic distance R is obtained. The model parameters in most
cases do not scale linearly with the lattice spacing and hence, their solution as a function of microscopic parameters reflects
only qualitatively the system evolution. Also, the atomic energy changes with R and therefore should be included in the model
analysis. The solutions in one dimension (D = 1) can be analyzed both rigorously (by making use of the Lieb–Wu solution) and compared with the approximate Gutzwiller
treatments. In higher dimensions (D = 2 and 3) only the latter approach is possible to implement within the scheme. The renormalized single particle wave functions
are almost independent of the choice of the scheme selected to diagonalize the Hamiltonian in the Fock space in D = 1 case.
For dimensions D > 1 the qualitative behavior is independent of the structure considered. The wave-function size increases
above the Mott-Hubbard localization threshold and gradually reaches the atomic limit value. The method can be extended to
other approximation schemes, as stressed at the end. 相似文献
7.
T. Saikawa A. Ferraz 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):65-74
A precursor effect on the Fermi surface in the two-dimensional Hubbard model at finite temperatures near the antiferromagnetic
instability is studied using three different itinerant approaches: the second order perturbation theory, the paramagnon theory
(PT), and the two-particle self-consistent (TPSC) approach. In general, at finite temperature, the Fermi surface of the interacting
electron systems is not sharply defined due to the broadening effects of the self-energy. In order to take account of those
effects we consider the single-particle spectral function A(, 0) at the Fermi level, to describe the counterpart of the Fermi surface at T = 0. We find that the Fermi surface is destroyed close to the pseudogap regime due to the spin-fluctuation effects in both
PT and TPSC approaches. Moreover, the top of the effective valence band is located around = (π/2,π/2) in agreement with earlier investigations on the single-hole motion in the antiferromagnetic background. A crossover
behavior from the Fermi-liquid regime to the pseudogap regime is observed in the electron concentration dependence of the
spectral function and the self-energy.
Received 8 September 2000 and Received in final form 20 December 2000 相似文献
8.
S. Sykora A. Hübsch K. W. Becker 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):181-187
We study the one-dimensional Holstein model of spinless fermions interacting
with dispersion-less phonons by using a recently developed projector-based
renormalization method (PRM). At half-filling the system shows a
metal-insulator transition to a Peierls distorted
state at a critical electron-phonon coupling where both phases
are described within the same theoretical framework.
The transition is accompanied by a phonon softening
at the Brillouin zone boundary and a gap in the electronic spectrum.
For different filling, the phonon softening appears away from the Brillouin
zone boundary and thus reflects a different type of broken symmetry state. 相似文献
9.
Y. Ōno R. Bulla A.C. Hewson M. Potthoff 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):283-290
We have studied the critical behaviour of a doped Mott insulator near the metal-insulator transition for the infinite-dimensional
Hubbard model using a linearized form of dynamical mean-field theory. The discontinuity in the chemical potential in the change
from hole to electron doping, for U larger than a critical value U
c, has been calculated analytically and is found to be in good agreement with the results of numerical methods. We have also
derived analytic expressions for the compressibility, the quasiparticle weight, the double occupancy and the local spin susceptibility
near half-filling as functions of the on-site Coulomb interaction and the doping.
Received 15 March 2001 and Received in final form 22 May 2001 相似文献
10.
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
11.
We calculate the Green function in the t-t
'-t
”-Jz model and analyze the deformation of the quantum Néel state in the presence of a moving hole. Solving the problem in a self-consistent
Born approximation and using Reiter's wave function we have found various spin correlation functions. We show that the different
sign of hopping elements between the hole- and electron-doped system of high- cuprates is responsible for the sharp difference of the polaron structure between the two systems with antiferromagnetism
stabilized in the electron-doped case by carriers moving mainly on one sublattice.
Received 11 January 2000 相似文献
12.
P. M.R. Brydon M. Gulácsi A. Bussmann-Holder 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(1):73-81
We present a non-perturbative study of an extended Falicov-Kimball model in
one
dimension. Working within the binary alloy interpretation, we include the
spin of the itinerant electrons and a Hubbard interaction to model the
inter-electron correlations. We derive an effective Ising model for the atomic
configuration in order to show how the Hubbard term affects the stability
of the phase separated states. Furthermore, we investigate the competition
between the Mott insulator state of the itinerant electrons and the
checkerboard phase of the spinless Falicov-Kimball model. 相似文献
13.
J. M.P. Carmelo K. Penc 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):477-499
We introduce a method that allows the evaluation of general expressions for the spectral
functions of the one-dimensional Hubbard model for all values of the on-site
electronic repulsion U. The spectral weights are expressed in terms of pseudofermion
operators such that the spectral functions can be written as a convolution of
pseudofermion dynamical correlation functions. Our results are valid for all finite
energy and momentum values and are used elsewhere in the study of the unusual
finite-energy properties of quasi-one-dimensional compounds and the new quantum systems
of ultra-cold fermionic atoms on an optical lattice. 相似文献
14.
15.
A. V. Lukoyanov V. V. Mazurenko V. I. Anisimov M. Sigrist T. M. Rice 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(2):205-207
We propose FeSb2 to be a nearly ferromagnetic small gap semiconductor, hence a direct analog
of FeSi. We find that despite different compositions and crystal structures,
in the local density approximation with on-site Coulomb repulsion correction (LDA+U) method
magnetic and semiconducting solutions for U=2.6 eV are energetically degenerate
similar to the case of FeSi. For both FeSb2 and FeSi (FeSi1-xGex alloys)
the underlying transition mechanism allows one to switch from a small gap semiconductor
to a ferromagnetic metal with magnetic moment ≈1 μB per Fe ion with external magnetic field. 相似文献
16.
T. Saikawa A. Ferraz 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):17-22
Dynamical properties of the spin and charge response functions in the doped two-dimensional Hubbard model are calculated by
taking into account the drastic separation of the single-particle spectral function into the low-energy coherent and high-energy
incoherent parts due to the strong Coulomb interaction. We show that this evolution of the electronic states is the origin
of the broad and structureless feature in the charge response function. In the weak coupling regime the low-energy enhancement
of the spin excitation is produced which can be explained within the random phase approximation. However, for the larger interaction
close to the antiferromagnetic Stoner condition, the low-energy intensity of the spin excitation is suppressed.
Received: 25 September 1997 / Revised: 19 December 1997 / Accepted: 9 January 1998 相似文献
17.
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
18.
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
19.
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
20.
A. Eilmes R.A. Römer M. Schreiber 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(2):229-234
We study the influence of many-particle interactions on a metal-insulator transition. We consider the two-interacting-particle
problem for onsite interacting particles on a one-dimensional quasiperiodic chain, the so-called Aubry-André model. We show
numerically by the decimation method and finite-size scaling that the interaction does not modify the critical parameters
such as the transition point and the localization-length exponent. We compare our results to the case of finite density systems
studied by means of the density-matrix renormalization scheme.
Received 28 June 2001 相似文献