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

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.

Generalized single-spin-flip dynamics for the Ising model and thermodynamic properties

1994 ◽  
Vol 49 (5) ◽  
pp. 3576-3579 ◽  
Author(s):  
A. M. Mariz ◽  
F. D. Nobre ◽  
C. Tsallis
Keyword(s):  
Ising Model ◽  
Thermodynamic Properties ◽  
Single Spin ◽  
Spin Flip

Determinant Monte Carlo for the Hubbard Model with Arbitrarily Gauged Auxiliary Fields

1992 ◽  
Vol 06 (05n06) ◽  
pp. 547-560 ◽  
Author(s):  
LIANG CHEN ◽  
A.-M.S. TREMBLAY
Keyword(s):  
Monte Carlo ◽  
Phase Space ◽  
Hubbard Model ◽  
Space Exploration ◽  
Field Method ◽  
Intermediate Coupling ◽  
Single Spin ◽  
First Time ◽  
Grand Canonical ◽  
Arbitrary Gauge

Monte Carlo methods for the Hubbard model rely on a Hubbard-Stratonovich (HS) decomposition (auxiliary field method) to perform importance sampling on classical variables. Freedom in the choice of the local HS fields can be formally seen as a gauge choice. While the choice of gauge does not influence observable quantities, it may influence intermediate quantities in the calculation, such as the famous “fermion sign”, and it may also influence the efficiency with which the algorithm explores phase space. The effect of arbitrary gauge choices on both aspects of the algorithm are investigated. It is found that in the single spin-flip determinantal approach, certain gauges lead to a better exploration of phase space. This improvement is demonstrated, in the intermediate coupling regime, by histograms which for the first time show the behavior expected from grand canonical simulations. It is also found that the improved phase space exploration can in practice offset the apparent disadvantage of a smaller fermion sign.

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