Phase separation, charge-transfer instability, and superconductivity in the three-band extended Hubbard model: Weak-coupling theory

1991 ◽  
Vol 43 (16) ◽  
pp. 13724-13727 ◽  
Author(s):  
Yunkyu Bang ◽  
G. Kotliar ◽  
C. Castellani ◽  
M. Grilli ◽  
R. Raimondi
Keyword(s):  
Phase Separation ◽  
Charge Transfer ◽  
Hubbard Model ◽  
Weak Coupling ◽  
Coupling Theory ◽  
Extended Hubbard Model ◽  
Weak Coupling Theory

PHASE SEPARATION AND SUPERCONDUCTIVITY IN THE U=∞ LIMIT OF THE EXTENDED MULTIBAND HUBBARD MODEL

1991 ◽  
Vol 05 (01n02) ◽  
pp. 309-321 ◽  
Author(s):  
M. Grilli ◽  
R. Raimondi ◽  
C. Castellani ◽  
C. Di Castro ◽  
G. Kotliar
Keyword(s):  
Phase Separation ◽  
Hubbard Model ◽  
Scattering Amplitude ◽  
Nearest Neighbour ◽  
Coupling Theory ◽  
Wave Channel ◽  
Large N ◽  
Expansion Technique ◽  
Weak Coupling Theory ◽  
A Charge

The three band Hubbard model with nearest neighbour repulsion is studied in the U=∞ limit using the large N expansion technique to order [Formula: see text]. A charge transfer (CT) instability is found like in weak coupling theory. However at small doping a major role is played by the Brinkman-Rice point. The CT instability is always associated with a diverging compressibility leading to a phase separation. The evaluation to order [Formula: see text] of the effective scattering amplitude in the Cooper channel shows the presence of superconducting instabilities in the s and d wave channel near the phase separation.

A WEAK COUPLING THEORY FOR La2CuO4: ln2–PARQUET APPROACH

1988 ◽  
Vol 02 (05) ◽  
pp. 667-677 ◽  
Author(s):  
I. E. Dzyaloshinskii ◽  
V. M. Yakovenko
Keyword(s):  
Fermi Surface ◽  
Hubbard Model ◽  
Weak Coupling ◽  
Weak Coupling Limit ◽  
Two Dimensional ◽  
Coupling Theory ◽  
Strong Difference ◽  
Effective Charges ◽  
Weak Coupling Theory

In the model of two-dimensional electrons with a square Fermi surface , ln 2-parquet equations are derived and numerically solved. It is suggested that this model can describe La 2 CuO 4 in the weak coupling limit. The main result is a strong difference between the Hubbard model with one charge and the model with four effective charges, describing an interaction of a general form.

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