Local magnetic properties of $$L\times L$$ L × L square lattice with an Extended Hubbard Model

2014 ◽  
Vol 47 (3) ◽  
pp. 523-528 ◽  
Author(s):  
A. Zouhair ◽  
S. Harir ◽  
M. Bennai ◽  
A. Migalska-Zalas ◽  
Y. Boughaleb
Keyword(s):  
Magnetic Properties ◽  
Hubbard Model ◽  
Square Lattice ◽  
Extended Hubbard Model

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.

Superconducting States with the Lattice Distortion in the Extended Hubbard Model

1997 ◽  
Vol 11 (09) ◽  
pp. 1153-1186
Author(s):  
Eiji Miyai ◽  
Masa-Aki Ozaki
Keyword(s):  
Hubbard Model ◽  
Order Parameter ◽  
Lattice Distortion ◽  
Mean Field ◽  
Square Lattice ◽  
Extended Hubbard Model ◽  
S Wave ◽  
Irreducible Components ◽  
Anisotropic Lattice ◽  
D Wave

We give group theoretical classification of superconducting (SC) states with a single SC order parameter in the extended Hubbard model with uniform lattice distortion on the two-dimensional square lattice, by using the mean field approach. We obtain two singlet SCs (s-wave and d-wave) and eight triplet SCs by decomposing the pairing interaction into irreducible components (A1g, B1g and Eu) of point symmetry D4h. We show that in the singlet SC state with a single SC order parameter (s-wave or d-wave) no anisotropic lattice distortion occurs. In the case of triplet SC states, two SC states among eight must be accompanied with anisotropic lattice distortion. The symmetry of SC order parameter uniquely determines the lattice symmetry. We have performed numerical calculations for these SC states, and shown the possibility that one of the SC states with anisotropic lattice distortion becomes most stable of all SC states in the extended Hubbard model. We also discuss singlet SC states with multiple SC order parameters (s-wave and d-wave). It is shown that the anisotropic distortion must occur in (s+d)-SC states and not in (s+id)-SC state.

PHASE DIAGRAM OF STRIPE ORDER IN THE EXTENDED HUBBARD MODEL

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3508-3513 ◽  
Author(s):  
MASARU KATO
Keyword(s):  
Hubbard Model ◽  
Coulomb Interaction ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Field Approximation ◽  
Square Lattice ◽  
Mean Field Approximation ◽  
Extended Hubbard Model ◽  
Stable States ◽  
Stripe Order

The extended Hubbard model with the nearest-neighbor Coulomb interaction on the square lattice is studied within the mean-field approximation. The stable states for 8×8 sites lattice with the periodic boundary condition and the electron filling n=0.875, as well as for 10×10 lattice and n=0.80, are obtained. For 8×8 lattice where quarter-filled straight stripe is expected because of the long-range Coulomb interaction, the cross stripe phases become stable.

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