Article,
Self-consistent summation of many-particle diagrams on the real frequency axis and its application to the FLEX approximation
Computer Physics Communications, 93 (2-3): 141--151 (February 1996)
Abstract
A new numerical method for the summation of Greens function diagrams
on the real frequency axis is presented. We apply our approach to
the fluctuation exchange approximation for the two-dimensional Hubbard
model, thereby taking full account of the momentum and frequency
dependence of the Greens functions and the resulting interactions.
Using the contour deformation technique in the complex frequency
plane, the self-energy integrals are evaluated by a combination of
Fourier and Laplace transformation and a subsequent application of
the Fast Fourier Transformation. In contrast to the imaginary frequency
approach, this method gives direct access to dynamical properties
with high energy resolution and good numerical stability. Results
for the electronic spectral density are shown which exhibit new fine
structure within the elementary excitations and in particular the
shadows of the Fermi surface, recently observed in high-Tc superconductors.
