scholarly journals Weak-coupling approach to the semi-infinite Hubbard model: non-locality of the self-energy

1997 ◽  
Vol 104 (2) ◽  
pp. 265-277 ◽  
Author(s):  
M. Potthoff ◽  
W. Nolting
Keyword(s):  
Hubbard Model ◽  
Weak Coupling ◽  
The Self ◽  
Self Energy ◽  
Coupling Approach ◽  
Non Locality

scholarly journals Self-Consistent Calculation of Particle-Hole Diagrams on the Matsubara Frequency: Flex Approximation

1997 ◽  
Vol 08 (05) ◽  
pp. 1145-1158
Author(s):  
J. J. Rodríguez-Núñez ◽  
S. Schafroth
Keyword(s):  
Hubbard Model ◽  
Imaginary Part ◽  
Chemical Potential ◽  
Order Approximation ◽  
The Self ◽  
Green Functions ◽  
Matsubara Frequency ◽  
Self Energy ◽  
Peak Structure ◽  
Self Consistent

We implement the numerical method of summing Green function diagrams on the Matsubara frequency axis for the fluctuation exchange (FLEX) approximation. Our method has previously been applied to the attractive Hubbard model for low density. Here we apply our numerical algorithm to the Hubbard model close to half filling (ρ =0.40), and for T/t = 0.03, in order to study the dynamics of one- and two-particle Green functions. For the values of the chosen parameters we see the formation of three branches which we associate with the two-peak structure in the imaginary part of the self-energy. From the imaginary part of the self-energy we conclude that our system is a Fermi liquid (for the temperature investigated here), since Im Σ( k , ω) ≈ w2 around the chemical potential. We have compared our fully self-consistent FLEX solutions with a lower order approximation where the internal Green functions are approximated by free Green functions. These two approches, i.e., the fully self-consistent and the non-self-consistent ones give different results for the parameters considered here. However, they have similar global results for small densities.

ANISOTROPIC PSEUDOGAP IN THE HALF-FILLING TWO-DIMENSIONAL HUBBARD MODEL AT FINITE TEMPERATURE

2000 ◽  
Vol 14 (21) ◽  
pp. 2271-2286
Author(s):  
TAIICHIRO SAIKAWA ◽  
ALVARO FERRAZ
Keyword(s):  
Fermi Surface ◽  
Fermi Level ◽  
Hubbard Model ◽  
Spectral Function ◽  
Density Of States ◽  
Spin Fluctuation ◽  
The Self ◽  
Two Dimensional ◽  
Self Energy ◽  
Half Filling

We have studied the pseudogap formation in the single-particle spectra of the half-filling two-dimensional Hubbard model. Using a Green's function with the one-loop self-energy correction of the spin and charge fluctuations, we have numerically calculated the self-energy, the spectral function, and the density of states in the weak-coupling regime at finite temperatures. Pseudogap formations have been observed in both the density of states and the spectral function at the Fermi level. The pseudogap in the spectral function is explained by the non-Fermi-liquid-like nature of the self-energy. The anomalous behavior in the self-energy is caused by both the strong antiferromagnetic spin fluctuation and the nesting condition on the non-interacting Fermi surface. In the present approximation, we find a logarithmic singularity in the integrand of the self-energy imaginary part. The pseudogap in the spectral function is highly momentum dependent on the Fermi surface. This anisotropy of the pseudogap is produced by the flatness of the band dispersion around the saddle point rather than the nesting condition on the Fermi level.

scholarly journals Momentum structure of the self-energy and its parametrization for the two-dimensional Hubbard model

2016 ◽  
Vol 93 (19) ◽  
Author(s):  
P. Pudleiner ◽  
T. Schäfer ◽  
D. Rost ◽  
G. Li ◽  
K. Held ◽  
...  
Keyword(s):  
Hubbard Model ◽  
The Self ◽  
Two Dimensional ◽  
Self Energy

scholarly journals CORRELATIONS AND THE RELATIVISTIC STRUCTURE OF THE NUCLEON SELF-ENERGY

1999 ◽  
Vol 08 (02) ◽  
pp. 179-196 ◽  
Author(s):  
H. MÜTHER ◽  
S. ULRYCH ◽  
H. TOKI
Keyword(s):  
Nuclear Matter ◽  
Particle Energy ◽  
The Self ◽  
Momentum Dependence ◽  
Hartree Fock ◽  
Self Energy ◽  
The Matrix ◽  
Lorentz Scalar ◽  
Bonn Potential ◽  
Non Locality

A key point of Dirac-Brueckner-Hartree-Fock calculations for nuclear matter is to decompose the self-energy of the nucleons into Lorentz scalar and vector components. A new method is introduced for this decomposition. It is based on the dependence of the single-particle energy on the small components in the Dirac spinors used to calculate the matrix elements of the underlying NN interaction. The resulting Dirac components of the self-energy depend on the momentum of the nucleons. At densities around and below the nuclear matter saturation density this momentum dependence is dominated by the non-locality of the Brueckner G matrix. At higher densities these correlation effects are suppressed and the momentum dependence due to the Fock exchange terms is getting more important. Differences between symmetric nuclear matter and neutron matter are discussed. Various versions of the Bonn potential are considered.

scholarly journals The Hubbard Model at Half-Filling, Part III: the Lower Bound on the Self-Energy

2005 ◽  
Vol 6 (3) ◽  
pp. 449-483 ◽  
Author(s):  
Stéphane Afchain ◽  
Jacques Magnen ◽  
Vincent Rivasseau
Keyword(s):  
Lower Bound ◽  
Hubbard Model ◽  
The Self ◽  
Self Energy ◽  
Half Filling
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