POSSIBLE COEXISTENCE OF ANTIFERROMAGNETISM AND SUPERCONDUCTIVITY IN THE HUBBARD MODEL

1988 ◽  
Vol 01 (09n10) ◽  
pp. 341-347 ◽  
Author(s):  
SHEN JUE-LIAN ◽  
SU ZHAO-BIN ◽  
DONG JIN-MING ◽  
YU LU
Keyword(s):  
Hubbard Model ◽  
High Temperature Superconductivity ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Antiferromagnetic Order ◽  
Effective Hamiltonian ◽  
Hamiltonian Approach ◽  
Theoretical Approaches ◽  
The Mean

The Hubbard model in the nearly half-filled case was studied in the mean field approximation using the effective Hamiltonian approach. Both antiferromagnetic order parameter and condensation of singlet pairs were considered. In certain parameter range the coexistence of antiferromagnetism and superconductivity is energetically favorable. Relations to the high temperature superconductivity and other theoretical approaches are also discussed.

scholarly journals Энергетический спектр и оптические свойства фуллерена C-=SUB=-80-=/SUB=-(I-=SUB=-h-=/SUB=-) в модели Хаббарда

2021 ◽  
Vol 129 (10) ◽  
pp. 1227
Author(s):  
А.В. Силантьев
Keyword(s):  
Group Theory ◽  
Hubbard Model ◽  
Symmetry Group ◽  
Mean Field ◽  
Analytical Form ◽  
Field Approximation ◽  
Energy Spectra ◽  
Mean Field Approximation ◽  
The Mean

The anticommutative Green’s functions were derived in an analytical form, and the energy spectra of С80 fullerene and endohedral Y3N@C80 fullerene of symmetry group Ih were obtained within the Hubbard model in the mean-field approximation. Using group theory methods, the classification of energy states was carried out, and the allowed transitions in the energy spectra of С80 and Y3N@C80 molecules of symmetry group Ih were determined.

scholarly journals ITINERANT AND LOCALIZED STATES IN STRONGLY CORRELATED SYSTEMS BY A MODIFIED MEAN-FIELD SLAVE-BOSON APPROACH

2001 ◽  
Vol 15 (05) ◽  
pp. 479-490 ◽  
Author(s):  
EMMANUELE CAPPELLUTI
Keyword(s):  
Hubbard Model ◽  
Mean Field ◽  
Field Approximation ◽  
Localized States ◽  
Mean Field Approximation ◽  
Strongly Correlated ◽  
Correlated Systems ◽  
The Mean ◽  
Hubbard Operators ◽  
Natural Way

The standard mean field slave-boson solution for the infinite-U Hubbard model is revised. A slightly modified version is proposed which includes properly the incoherent contribution of the localized states. In contrast to the standard mean field result, this new proposed solution defines a unique spectral function to be used in the calculation of local and not local quantities, and satisfies the correct thermodynamic relations. The same approach is applied also to the mean field approximation in terms of Hubbard operators. As a byproduct of this analysis, Luttinger's theorem is shown to be fulfilled in a natural way.

scholarly journals Энергетический спектр и оптические свойства фуллерена С-=SUB=-36-=/SUB=- в модели Хаббарда

2019 ◽  
Vol 127 (8) ◽  
pp. 191
Author(s):  
А.В. Силантьев
Keyword(s):  
Group Theory ◽  
Hubbard Model ◽  
Symmetry Group ◽  
Mean Field ◽  
Field Approximation ◽  
Energy Spectra ◽  
Mean Field Approximation ◽  
Endohedral Fullerene ◽  
The Mean ◽  
Energy States

AbstractThe anticommutator Green’s functions and the energy spectra of fullerene С_36 and endohedral fullerene La@C_36, with both of them belonging to the D _6 h symmetry group, are obtained analytically within the Hubbard model in the mean-field approximation. Using group-theory methods, their energy states are classified and allowed transitions in the energy spectra of the С_36 and La@C_36 molecules, both belonging to the D _6 h symmetry group, are determined.

DISCUSSION ON THE MEAN FIELD APPROXIMATION IN THE RVB THEORY

1988 ◽  
Vol 02 (10) ◽  
pp. 1205-1209 ◽  
Author(s):  
R.B. TAO ◽  
X. HU ◽  
M. SUZUKI
Keyword(s):  
Hubbard Model ◽  
Strong Correlation ◽  
Magnetic System ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Hubbard Hamiltonian ◽  
Half Filling ◽  
The Mean

Baskaran’s mean field approximation of the Hubbard Hamiltonian with strong correlation and half-filling is discussed. Our calculations show that his decoupling of the Hamiltonian is not permissible in the half-filling case and that it destroys the equivalence of the Hubbard model to the Heisenberg magnetic system and violates some spin-spin relations.

scholarly journals The Combined Effect of Rotation and Magnetic Field on Finite-Amplitude Thermal Convection

1973 ◽  
Vol 26 (5) ◽  
pp. 617 ◽  
Author(s):  
R Van der Borght ◽  
JO Murphy
Keyword(s):  
Magnetic Field ◽  
Mean Field ◽  
Field Approximation ◽  
Finite Amplitude ◽  
Combined Effect ◽  
Mean Field Approximation ◽  
Free Boundaries ◽  
Wide Range ◽  
The Mean ◽  
Basic Equations

The combined effect of an imposed rotation and magnetic field on convective transfer in a horizontal Boussinesq layer of fluid heated from below is studied in the mean field approximation. The basic equations are derived by a variational technique and their solutions are then found over a wide range of conditions, in the case of free boundaries, by numerical and analytic techniques, in particular by asymptotic and perturbation methods. The results obtained by the different techniques are shown to be in excellent agreement. As for the linear theory, the calculations predict that the simultaneous presence' of a magnetic field and rotation may produce conflicting tendencies.

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