Higher-order correlation effects to the solution of the Hubbard model

2000 ◽  
Vol 61 (8) ◽  
pp. 5158-5168 ◽  
Author(s):  
Hong-Gang Luo ◽  
Shun-Jin Wang
Keyword(s):  
Hubbard Model ◽  
Higher Order ◽  
Correlation Effects

η-PAIRING SUPERCONDUCTIVITY IN THE NEGATIVE-U HUBBARD MODEL: EFFECT OF FLUCTUATIONS AND DISORDER

1994 ◽  
Vol 08 (15) ◽  
pp. 2041-2058
Author(s):  
JÜRGEN STEIN
Keyword(s):  
Phase Diagram ◽  
Asymptotic Expansion ◽  
Hubbard Model ◽  
Strong Coupling ◽  
Mean Field ◽  
Higher Order ◽  
Field Phase ◽  
Effective Pair ◽  
The Mean ◽  
Pair Hopping

We have studied the influence of singular fluctuations around the mean-field solution as well as higher order contributions to the geometry controlled asymptotic expansion of the propagators on η-pairing superconductivity in the strong coupling negative-U Hubbard model in the presence of unpaired electrons. The modifications of the mean-field results due to the introduction of disorder and allowance for finite U are also calculated. Besides the singularities already present in the O(2) nonlinear σ-model we find a filling-depending singular depression of the repulsive effective pair-hopping interaction which strongly alters the mean-field phase diagram and appears to suppress the η-pairing phase near the band edges.

FERMI SYSTEMS, HUBBARD MODEL AND A SYMBOLICC++ IMPLEMENTATION

2001 ◽  
Vol 12 (02) ◽  
pp. 235-245 ◽  
Author(s):  
YORICK HARDY ◽  
WILLI-HANS STEEB
Keyword(s):  
Hubbard Model ◽  
Computer Algebra ◽  
Matrix Representation ◽  
Higher Order ◽  
Fermi Systems ◽  
The Matrix ◽  
Constants Of Motion

We show how the anticommutation relations for Fermi operators can be implemented with computer algebra using SymbolicC++. We describe applications to the Hubbard model. An important identity for Fermi operators is proved. Then, we test for higher order constants of motion for the Hubbard model. Finally, the matrix representation for the four point Hubbard model is calculated.

Wave-number dependence of the static screening function of an interacting electron gas. II. Higher-order exchange and correlation effects

1970 ◽  
Vol 48 (2) ◽  
pp. 167-181 ◽  
Author(s):  
D. J. W. Geldart ◽  
Roger Taylor
Keyword(s):  
Density Dependence ◽  
Ground State ◽  
Electron Gas ◽  
Perturbation Expansion ◽  
Interpolation Formula ◽  
Higher Order ◽  
Wave Number ◽  
Correlation Effects ◽  
Many Body ◽  
Static Screening

An interpolation formula is suggested for the wave-number and density dependence of the static screening function for an interacting electron gas in its ground state. The approximate screening function simulates a number of properties of the exact screening function which have been established by analysis of its many-body perturbation expansion. The accuracy of the interpolation formula is discussed and is considered to be adequate for practical calculations in the range of intermediate metallic densities.

Perturbational treatment of correlation effects in the Hubbard model

1990 ◽  
Vol 41 (1) ◽  
pp. 413-427 ◽  
Author(s):  
G. Bulk ◽  
R. J. Jelitto
Keyword(s):  
Hubbard Model ◽  
Correlation Effects
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