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Alexei Sherman 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(4):91
Using the strong coupling diagram technique, the energy spectrum of the three-bandHubbard model is investigated. In these calculations, the series in powers of thecopper-oxygen hybridization for the irreducible part is approximated by two lowest-orderterms. For parameters of hole-doped cuprates the calculated energy spectrum consists oflower and upper Hubbard subbands of predominantly copper nature, oxygen bands with someadmixture of copper states and the Zhang-Rice states of mixed nature. The spectrumcontains two pseudogaps, the lower of which separates the Hubbard subband from Zhang-Riceand oxygen bands. The pseudogaps arise due to multiple reabsorption of carriers in stateswith double occupancy of sites by holes or electrons. 相似文献
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Thermodynamic properties of the half-filled-band Hubbard model are calculated in the strong-coupling regime for a simple cubic structure, using the Bogoliubov variational principle. When the Coulomb-interactionV
o exceeds the bandwidthJ, we find a phase transition from a condensed phase of itinerant electrons into a state of localized ones at a transition temperature which exhibits the asymptotic behaviourT
0J
2/V
0 at largeV
0. 相似文献
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Thermodynamic properties of the half-filled-band Hubbard model are calculated in the strong-coupling regime for a simple cubic structure, using the Bogoliubov variational principle. When the Coulomb-interactionV
o exceeds the bandwidthJ, we find a phase transition from a condensed phase of itinerant electrons into a state of localized ones at a transition temperature which exhibits the asymptotic behaviourT
0J
2/V
0 at largeV
0. 相似文献
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From a new variational approach to the Hubbard model, communicated previously [1], we derive the magnetic strong-coupling properties for the half filled band case of the Hubbard model in simple cubic lattices. The transition temperature from an AB-antiferromagnetic to a paramagnetic state, the sublattice magnetization and the localization of magnetic moments are investigated in detail. Near the strong coupling limit the results become asymptotically exact in a molecular field sense but they look reasonable even outside this asymptotic region. 相似文献
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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
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G. Pawłowski 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):471-479
The extended Hubbard model in the atomic limit (AL-EHM) on a square lattice with periodic boundary conditions is studied with
use of the Monte Carlo (MC) method. Within the grand canonical ensemble the phase and order-order boundaries for charge orderings
are obtained. The phase diagrams include three types of charge ordered phases and the nonordered phase. The system exhibits
very rich structure and shows unusual multicritical behavior.
In the limiting case of tij=0, the EHM is equivalent to the pseudospin model with single-ion anisotropy
, exchange interaction W in an effective magnetic field
. This classical spin model is analyzed using the MC method for the canonical ensemble. The phase diagram is compared with
the known results for the Blume-Capel model. 相似文献
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S. V. Lovtsov N. M. Plakida V. Yu. Yushankhai 《Zeitschrift für Physik B Condensed Matter》1991,82(1):1-4
A two-band Hubbard model for highly hybridized copper 3d(x
2–y
2) and oxygen 2p(x,y) electrons in CuO2 plane with strong Coulomb repulsion at copper sites is considered. A real-space pairing mechanism induced by antiferromagnetic interaction of Kondo type is treated. To avoid the Gutzwiller approximation the projection technique for two-time Green functions for Hubbard operators is employed. It is shown that due to rigorous restriction of no double occupancy at copper sites the exchange-mediatedp-d pairing with a site-independent gap function isabsent. 相似文献
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The three-band Hubbard model — both pure and with static non-magnetic impurities — has been studied within a self-consistent
numerical Hartree-Fock (HF) scheme. The system shows nesting properties only in the absence of direct O-O hopping. Spin excitations
in the system are gapless with the existence of a Goldstone mode in the broken-symmetry state. The variation of spinwave velocity
with Cu-site Coulomb repulsion shows a (1/(2U
d)+(1/Δ)) dependence in the strong-coupling limit. Each non-magnetic impurity in the system gives rise to two gap states for
a particular spin and the local moment produced is robust even at finite concentration of mobile hole doping. The gapless
Goldstone mode is preserved even in case of unequal concentration of impurities on the two sublattices. 相似文献
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The three-band Emery model is reduced to a single-particle quantum model of
Falicov-Kimball type, by allowing only up-spins to hop, and forbidding double
occupation by projection. It is used to study the effects of geometric
obstruction on mobile fermions in thermodynamic equilibrium. For low hopping
overlap, there appears a plateau in the entropy, due to charge correlations,
and related to real-space disorder. For large overlap, the equilibrium
thermopower susceptibility remains anomalous, with a sign opposite to the one
predicted from the single-particle density of states. The heat capacity and
non-Fermi liquid response are discussed in the context of similar results in
the literature. All results are obtained by evaluation of an effective
single-particle free-energy operator in closed form. The method to obtain this
operator is described in detail. 相似文献
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We discuss the rotational limit of the interacting boson model and bring attention to the possible existence of an unbroken SU(3) symmetry. We derive, within the framework of this symmetry, several analytic relations for energies and electromagnetic transition rates. 相似文献
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