INTERACTION BETWEEN O QUASIPARTICLES IN CuO2-BASED SUPERCONDUCTORS

1991 ◽  
Vol 05 (12) ◽  
pp. 2109-2123 ◽  
Author(s):  
A. A. ALIGIA
Keyword(s):  
Hubbard Model ◽  
Bound States ◽  
Nearest Neighbor ◽  
Effective Interaction ◽  
Effective Hamiltonian ◽  
Extended Hubbard Model

We consider the extended Hubbard model including repulsion Upd between nearest-neighbor Cu and O holes. In the limit of strong intra-atomic correlations and weak hopping, we derive an effective Hamiltonian for the O holes. This Hamiltonian contains interactions between O holes with a common nearest-neighbor Cu ion. The effective interaction between two holes is repulsive for small Upd and attractive otherwise. Bound states between two holes exist only if the effective interaction between them is sufficiently large and negative.

TWO-DIMENSIONAL QUARTER-FILLED EXTENDED HUBBARD MODEL AT STRONG COUPLING

2005 ◽  
Vol 19 (01n03) ◽  
pp. 213-216
Author(s):  
W. F. LEE ◽  
H. Q. LIN
Keyword(s):  
Hubbard Model ◽  
Correlation Functions ◽  
Nearest Neighbor ◽  
Spin Correlation ◽  
Perturbation Approach ◽  
Effective Hamiltonian ◽  
Two Dimensional ◽  
Extended Hubbard Model ◽  
Neighbor Interaction ◽  
Electron Hopping

In this paper, we generalized the perturbation approach to study the quasi-two-dimension extended Hubbard model. This model is characterizing by intra-chain electron hopping t, on-site Column interaction U, nearest-neighbor interaction V, and inter-chain electron hopping t′ and nearest-neighbor interaction V′. An effective Hamiltonian up to sixth-order in t/U, t/V, t/V′, t′/U, t′/V and t′/V′ expansion was obtained and the spin-spin correlation functions were calculated. We presented results for t=t′, V=V′.

Quarter-Filled Extended Hubbard Model at Strong Coupling

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3339-3342 ◽  
Author(s):  
W. F. Lee ◽  
H. Q. Lin
Keyword(s):  
Hubbard Model ◽  
Strong Coupling ◽  
Coulomb Interaction ◽  
State Energy ◽  
Nearest Neighbor ◽  
Spin Correlation ◽  
Perturbation Approach ◽  
Effective Hamiltonian ◽  
Extended Hubbard Model ◽  
One Dimensional

We apply a perturbation approach to study the quarter-filled extended Hubbard model at strong coupling limit. An effective Hamiltonian up to sixth order in t/U and t/V (t defines electron hopping, U defines on-site Coulomb interaction, and V defines nearest-neighbor Coulomb interaction) for one-dimensional chains was obtained. The spin-spin correlation functions were involved, which can be obtained after comparing to the ground state energy numerically obtained from the phase diagram.

SUPERCONDUCTING CLASSES IN THE EXTENDED HUBBARD MODEL

1996 ◽  
Vol 10 (12) ◽  
pp. 1397-1423 ◽  
Author(s):  
MASA-AKI OZAKI ◽  
EIJI MIYAI ◽  
TOMOAKI KONISHI ◽  
KAORU HANAFUSA
Keyword(s):  
Hubbard Model ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Square Lattice ◽  
Extended Hubbard Model ◽  
S Wave ◽  
Ferromagnetic Order ◽  
Numerical Studies ◽  
The Mean

This paper describes group theoretical classification of superconducting states (SC) in the extended Hubbard model with on-site repulsion (U), nearest neighbor attraction (V) and nearest neighbour exchange interaction (J) on the two-dimensional square lattice using the mean field approach. By decomposing the pairing interaction into irreducible parts; A1g, B1g and Eu of D4h point symmetry, we have derived two singlet SCs (s-wave and d-wave) from A1g and B1g, eight triplet SCs from Eu. The first three types of triplet SC have pairing by electrons with antiparallel spin, the second two types have pairing by electrons with equal spin and the last three types are non-unitary and have pairing by only up-spin electrons. We showed that three non-unitary states have to be accompanied with a ferromagnetic order from the structure of the maximal little groups. We performed numerical studies for these SCs. For parameters and electron density favorable for the ferromagnetic order, a non-unitary SC coexistent with ferromagnetism is most stable.

GROUND STATE OF THE 2D EXTENDED HUBBARD MODEL WITH MORE THAN NEAREST-NEIGHBOR INTERACTIONS

2012 ◽  
Vol 26 (29) ◽  
pp. 1250156 ◽  
Author(s):  
S. HARIR ◽  
M. BENNAI ◽  
Y. BOUGHALEB
Keyword(s):  
Phase Diagram ◽  
Hubbard Model ◽  
Ground State ◽  
State Energy ◽  
Nearest Neighbor ◽  
Finite Size ◽  
Square Lattice ◽  
Extended Hubbard Model ◽  
Eigenvalues And Eigenvectors ◽  
Repulsion Energy

We investigate the ground state phase diagram of the two dimensional Extended Hubbard Model (EHM) with more than Nearest-Neighbor (NN) interactions for finite size system at low concentration. This EHM is solved analytically for finite square lattice at one-eighth filling. All eigenvalues and eigenvectors are given as a function of the on-site repulsion energy U and the off-site interaction energy Vij. The behavior of the ground state energy exhibits the emergence of phase diagram. The obtained results clearly underline that interactions exceeding NN distances in range can significantly influence the emergence of the ground state conductor–insulator transition.

scholarly journals SUPERCONDUCTING ORDER PARAMETERS IN THE EXTENDED HUBBARD MODEL: A SIMPLE MEAN-FIELD STUDY

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2371-2383 ◽  
Author(s):  
J. S. THAKUR ◽  
M. P. DAS
Keyword(s):  
Hubbard Model ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Order Parameters ◽  
Square Lattice ◽  
Extended Hubbard Model ◽  
Self Consistent ◽  
Frame Work ◽  
Field Formalism ◽  
Superconducting Pairing

The extended Hubbard model with nearest neighbor hopping and intersite interaction for a 2D square lattice has been studied within the frame work of a simple mean-field formalism. The self-consistent solutions of superconducting order parameters have been obtained for various fillings. The results indicate that superconducting pairing occurs on doping for the repulsive on-site U and attractive nearest neighbor V.

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