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1.
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
2.
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
3.
D. Meyer W. Nolting 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):385-395
We compare different approximation schemes for investigating ferromagnetism in the periodic Anderson model. The use of several
approximations allows for a detailed analysis of the implications of the respective methods, and also of the mechanisms driving
the ferromagnetic transition. For the Kondo limit, our results confirm a previously proposed mechanism leading to ferromagnetic
order, namely an RKKY exchange mediated via the formation of Kondo screening clouds in the conduction band. The contrary case is found in the intermediate-valence regime.
Here, the bandshift correction ensuring a correct high-energy expansion of the self-energy is essential. Inclusion of damping
effects reduces stability of the ferromagnetic phase.
Received 5 June 2000 and Received in final form 3 August 2000 相似文献
4.
B. Andraka R. Pietri S.G. Thomas G.R. Stewart E.-W. Scheidt T. Schreiner 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):55-59
A comprehensive study of the relationship between the electronic specific heat coefficient () and the temperature square coefficient (A) of the electrical resistivity for a single, cubic, heavy fermion alloy system, UPt5-xAux is presented. In this alloy system, whose low temperature properties are consistent with the Fermi-liquid behavior, varies by more than a factor of 10 while the corresponding A coefficient changes by a factor larger than 200. A tracks changes in fairly well, but , postulated to have a universal value for heavy fermions, is not constant and varies from about 10-6 (x = 0, 0.5) to 10-5
cm (mol K/mJ)2 (x
> 1.1), thus from a value typical of transition metals to that characteristic of other heavy fermion compounds. We have found a
correlation between and magnetic characteristics such as the paramagnetic Curie-Weiss temperature and the low temperature magnetic susceptibility
divided by .
Received 29 January 1999 相似文献
5.
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
6.
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
7.
P. Schlottmann A.A. Zvyagin 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):325-335
We consider the one-dimensional t
-
J model, which consists of electrons with spin S on a lattice with nearest neighbor hopping t constrained by the excluded multiple occupancy of the lattice sites and spin-exchange J between neighboring sites. The model is integrable at the supersymmetric point, J
=
t. Without spoiling the integrability we introduce an Anderson-like impurity of spin S (degenerate Anderson model in the limit), which interacts with the correlated conduction states of the host. The lattice model is defined by the scattering
matrices via the Quantum Inverse Scattering Method. We discuss the general form of the interaction Hamiltonian between the impurity and
the itinerant electrons on the lattice and explicitly construct it in the continuum limit. The discrete Bethe ansatz equations
diagonalizing the host with impurity are derived, and the thermodynamic Bethe ansatz equations are obtained using the string
hypothesis for arbitrary band filling as a function of temperature and external magnetic field. The properties of the impurity
depend on one coupling parameter related to the Kondo exchange coupling. The impurity can localize up to one itinerant electron
and has in general mixed valent properties. Groundstate properties of the impurity, such as the energy, valence, magnetic
susceptibility and the specific heat coefficient, are discussed. In the integer valent limit the model reduces to a Coqblin-Schrieffer impurity.
Received: 31 December 1997 / Accepted: 17 March 1998 相似文献
8.
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
9.
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
10.
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
11.
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
12.
P. Bonville E. Vincent E. Bauer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):363-369
We present measurements in the YbCu5-xAlx series, down to the 50 mK range, using 170Yb M?ssbauer absorption spectroscopy and magnetisation measurements. In this series, the hybridisation between the Yb 4
f electrons and the conduction electrons is known to decrease as the Al content x increases. We apply the variational solution of the impurity Kondo problem to the interpretation of our data. We show that
the Kondo temperature can be derived from the measured 4
f quadrupole moment and, for the magnetically ordered compounds (), we obtain the exchange energy as a function of the Al content. Our findings are in general agreement with Doniach's model
describing the onset of magnetic ordering according to the relative values of the Kondo and exchange energy scales.
Received 16 April 1998 相似文献
13.
M.A. Continentino 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):31-35
Recently we have shown that a one-parameter scaling, , describes the physical behavior of several heavy fermions in a region of their phase diagram. In this paper we fully characterize
this region, obtaining the uniform susceptibility, the resistivity and the specific heat in terms of the coherence temperature
. This allows for an explicit evaluation of the Wilson and the Kadowaki-Woods ratios in this regime. These quantities turn
out to be independent of the distance to the quantum critical point (QCP). The theory of the one-parameter scaling corresponds to a local interacting model. Although
spatial correlations are irrelevant in this case, time fluctuations are critically correlated as a consequence of the quantum
character of the transition.
Received 23 December 1998 and Received in final form 10 June 1999 相似文献
14.
15.
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
16.
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
17.
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
18.
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
19.
M. Capone M. Grilli W. Stephan 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):551-557
We investigate polaron formation in a many-electron system in the presence of a local repulsion sufficiently strong to prevent
local-bipolaron formation. Specifically, we consider a Hubbard-Holstein model of interacting electrons coupled to dispersionless
phonons of frequency . Numerically solving the model in a small one-dimensional cluster, we find that in the nearly adiabatic case , the necessary and sufficient condition for the polaronic regime to occur is that the energy gain in the atomic (i.e., extremely localized) regime overcomes the energy of the purely electronic system . In the antiadiabatic case, , polaron formation is instead driven by the condition of a large ionic displacement (g being the electron-phonon coupling). Dynamical properties of the model in the weak and moderately strong coupling regimes
are also analyzed.
Received 15 February 1999 相似文献
20.
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