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

J. J. Rodríguez-Núñez () and S. Schafroth ()
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J. J. Rodríguez-Núñez: Instituto de Física, Universidade Federal Fluminense, Av. Litorânea S/N, Boa Viagem, 24210-340 Niterói RJ, Brazil
S. Schafroth: Physik–Institut der Universität Zürich, Winterthurerstrasse 190, CH–8057 Zürich, Switzerland

International Journal of Modern Physics C (IJMPC), 1997, vol. 08, issue 05, 1145-1158

Abstract: 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 forT/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 ImΣ(k, ω) ≈ w2around 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.

Keywords: FLEX; Matsubara Frequency; Particle-Hole; 74.20.-Fg; 74.10.-z; 74.60.-w; 74.72.-h (search for similar items in EconPapers)
Date: 1997
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DOI: 10.1142/S0129183197001016

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