Stability of the ferromagnetic state with respect to a single spin flip: Variational calculations for theU=∞ Hubbard model on the square lattice

1990 ◽  
Vol 41 (7) ◽  
pp. 4842-4845 ◽  
Author(s):  
Anthony G. Basile ◽  
Veit Elser
Keyword(s):  
Hubbard Model ◽  
Ferromagnetic State ◽  
Square Lattice ◽  
Single Spin ◽  
Spin Flip ◽  
Variational Calculations

SINGLE SPIN FLIP IN THE INFINITE U HUBBARD MODEL: HUBBARD OPERATORS, THREE-BODY FADEEV EQUATIONS AND GUTZWILLER WAVE FUNCTIONS

1989 ◽  
Vol 03 (12) ◽  
pp. 1809-1832 ◽  
Author(s):  
Andrei E. Ruckenstein ◽  
Stefan Schmitt-Rink
Keyword(s):  
Hubbard Model ◽  
Mean Field Theory ◽  
Mean Field ◽  
Ferromagnetic State ◽  
Physical Content ◽  
Single Spin ◽  
Hartree Fock ◽  
Spin Flip ◽  
Three Body ◽  
Hubbard Operators

We investigate a recently proposed many-body theory for composite (Hubbard) operators (A.E. Ruckenstein and S. Schmitt-Rink, Phys. Rev. B38, 7188 (1988)) in the context of the problem of a single spin flip in the saturated ferromagnetic state of the infinite U Hubbard model. We prove that the suitably defined strong coupling Hartree-Fock mean field theory leads to results identical to those obtained from the Gutzwiller wave function through exact evaluation of the kinetic energy. Most interestingly, we also show how exactly the same results can be obtained starting from the weak coupling limit by solving analytically the three-body t-matrix (Fadeev) equations in the infinite U limit. This work also sheds light on the physical content of slave boson approximations to which our approach was previously shown to be equivalent in the limit of large spin or orbital degeneracy. For the single spin flip problem we compare our results with those obtained by Bethe-Goldstone perturbation theory, Bethe Ansatz in one dimension, and exact diagonalization studies.

scholarly journals Exact Single Spin Flip for the Hubbard Model ind=∞

1996 ◽  
Vol 77 (17) ◽  
pp. 3629-3632 ◽  
Author(s):  
Götz S. Uhrig
Keyword(s):  
Hubbard Model ◽  
Single Spin ◽  
Spin Flip

scholarly journals Scaling properties of the ferromagnetic state in the Hubbard model

1994 ◽  
Vol 50 (17) ◽  
pp. 12991-12994 ◽  
Author(s):  
K. Kusakabe ◽  
H. Aoki
Keyword(s):  
Hubbard Model ◽  
Ferromagnetic State ◽  
Scaling Properties

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.

Hubbard model in the ferromagnetic state. Dimer and trimer approach

2005 ◽  
Vol 242 (2) ◽  
pp. 337-341 ◽  
Author(s):  
M. Matlak ◽  
T. Słomska ◽  
B. Grabiec
Keyword(s):  
Hubbard Model ◽  
Ferromagnetic State
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