共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
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
3.
P. Farkašovský 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(2):209-215
A new numerical method is used to study the ground-state properties of the spinless Falicov-Kimball model in one and two dimensions.
The resultant solutions are used to examine the phase diagram of the model as well as possibilities for valence and metal-insulator
transitions. In one dimension a comprehensive phase diagram of the model is presented. On the base of this phase diagram,
the complete picture of valence and metal-insulator transitions is discussed. In two dimensions the structure of ground-state
configurations is described for intermediate interactions between f and d electrons. In this region the phase separation and metal-insulator transitions are found at low f-electron concentrations. It is shown that valence transitions exhibit a staircase structure.
Received 20 October 2000 相似文献
4.
C. Schneider G. Czycholl 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):43-50
We study the (spinless) Falicov-Kimball model extended by a finite band width (hopping t
f
) of the localized (f-) electrons in infinite dimensions in the weak-coupling limit of a small local interband Coulomb correlation U for half filling. In the case of overlapping conduction- and f-bands different kinds of ordered solutions are possible, namely charge-density wave (CDW) order, electronic ferroelectricity
(EFE) and electronic antiferroelectricity (EAFE). The order parameters are calculated as a function of the model parameters
and of the temperature. There is a first-order phase transition from the CDW-phase to the EFE- or EAFE-phase. The total energy
is calculated to determine the thermodynamically stable solution. The quantum phase diagrams are calculated. 相似文献
5.
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
6.
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
7.
8.
S.G. Mishra P.A. Sreeram 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):287-291
Specific heat versus temperature curves for various pressures, or magnetic fields (or some other external control parameter) have been seen to
cross at a point or in a very small range of temperatures in many correlated fermion systems. We show that this behavior is
related to the possibility of existence of a quantum critical point. Vicinity to a quantum critical point in these systems
leads to a crossover from quantum to classical fluctuation regime at some temperature . The temperature at which the curves cross turns out to be near this crossover temperature. We have discussed the case of
the normal phase of liquid Helium three and the heavy fermion systems CeAl3 and UBe13 in detail within the spin fluctuation theory, a theory which inherently contains a low energy scale which can be identified
with . When the crossover scale is a homogeneous function of these control parameters there is always crossing at a point. We also
mention other theories exhibiting a low energy scale near a quantum critical point and discuss this phenomenon in those theories.
Received 25 June 1999 相似文献
9.
Y. Nishiyama 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):547-554
To investigate the influence of electronic interaction on the metal-insulator transition (MIT), we consider the Aubry-André
(or Harper) model which describes a quasiperiodic one-dimensional quantum system of non-interacting electrons and exhibits
an MIT. For a two-particle system, we study the effect of a Hubbard interaction on the transition by means of the transfer-matrix
method and finite-size scaling. In agreement with previous studies we find that the interaction localizes some states in the
otherwise metallic phase of the system. Nevertheless, the MIT remains unaffected by the interaction. For a long-range interaction,
many more states become localized for sufficiently large interaction strength and the MIT appears to shift towards smaller
quasiperiodic potential strength.
Received 17 August 1998 相似文献
10.
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
11.
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
12.
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
13.
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
14.
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
15.
P. Bonville J. A. Hodges Z. Hossain R. Nagarajan S. K. Dhar L. C. Gupta E. Alleno C. Godart 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(3):377-383
We present magnetic properties of the three-band Hubbard model in the para- and antiferromagnetic phase on a hypercubic lattice
calculated with the Dynamical Mean-Field Theory (DMFT). To allow for solutions with broken spin-symmetry we extended the approach
to lattices with AB-like structure. Above a critical sublattice magnetization one can observe rich structures in the spectral-functions similar to the t-J model which can be related to the well known bound states for one hole in the Neél-background. In addition to the one-particle
properties we discuss the static spin-susceptibility in the paramagnetic state at the points and for different dopings . The -T-phase-diagram exhibits an enhanced stability of the antiferromagnetic state for electron-doped systems in comparison to hole-doped.
This asymmetry in the phase diagram is in qualitative agreement with experiments for high-Tc materials.
Received: 28 May 1998 / Revised and Accepted: 14 September 1998 相似文献
16.
B.M. Letfulov 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):195-203
This paper gives a simplified model of the double exchange which is a kind of indirect exchange interaction between localized
magnetic moments. The presented model is solved exactly in the case of infinite - dimensional space. Equations for single-particle
Green's function and magnetization of the localized spins subsystem are obtained. It is shown that our simple double exchange
model reveals an instability to the ferromagnetic ordering of localized moments. Magnetic and electric properties of this
system on Bethe lattice with are investigated in detail.
Received: 24 January 1997 / Revised: 14 February 1997 / Received in final form: 18 August 1997 / Accepted: 25 August 1997 相似文献
17.
A. Takahashi H. Shiba 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):413-417
The optical absorption in ferromagnetic metal La1-xSrxMnO3 is anomalous; it has a wide-range absorption up to about 1 eV even at zero temperature. Since 3d electrons in La1-xSrxMnO3 partially fill doubly degenerate eg orbitals, the orbital degrees of freedom are crucial to understand this metallic system. We argue that the interband transition
within eg orbitals is important in the optical absorption. The optical spectrum is modified also by the inter-orbital Coulomb interaction.
We have examined perturbatively the effect of the Coulomb interaction on the spectrum. Available experiments are discussed
by comparing with the present results.
Received: 13 February 1998 / Accepted: 17 March 1998 相似文献
18.
A. K. Zhuravlev V. Yu. Irkhin M. I. Katsnelson 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):377-382
Using the numerical renormalization group method, the dependences on
temperature of the magnetic susceptibility χ(T) and specific heat C(T)
are obtained for the single-impurity Anderson model with inclusion of
d-f the Coulomb interaction. It is shown that the exciton effects
caused by this effect (charge fluctuations) can significantly change the
behaviour of C(T) in comparison with the standard Anderson model at
moderately low temperatures, whereas the behaviour of χ(T) remains nearly
universal. The ground-state and temperature-dependent renormalizations of the
effective hybridization parameter and f-level position caused by the
d-f interaction are calculated, and satisfactory agreement with the
Hartree-Fock approximation is derived. 相似文献
19.
M.B. Zölfl Th. Maier Th. Pruschke J. Keller 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):47-53
We study one-particle spectra and the electronic band-structure of a CuO
2
-plane within the three-band Hubbard model. The Dynamical Mean-Field Theory (DMFT) is used to solve the many particle problem.
The calculations show that the optical gap is given by excitations from the lower Hubbard band into the so called Zhang-Rice singlet band. The optical gap turns out to be considerably smaller than the bare charge transfer energy () for a typical set of parameters, which is in agreement with experiment. We also investigate the dependence of the shape
of the Fermi surface on the different hopping parameters t
CuO and t
OO. A value t
OO
/
t
CuO
>0 leads to a Fermi surface surrounding the M point.
Received 21 September 1998 and Received in final form 8 June 1999 相似文献
20.
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