TITLE:
Diagrammatic Iteration Approach to Electron Correlation Effects
AUTHORS:
J. D. Fan, Y. M. Malozovsky
KEYWORDS:
Electron Correlation Effect, Diagrammatic Iteration Approach, Superconductivity, Condensed Matter Physics
JOURNAL NAME:
Journal of Modern Physics,
Vol.5 No.7,
April
30,
2014
ABSTRACT: Electron
correlation is a measure of the errors that are inherent in the Hartree-Fock theory
or orbital models. When the electron density is high, correlation is weak and
the traditional electronic theory works well. However, at a low density of
electrons correlation effects become strong and the traditional theory fails to
describe the electron system correctly. Therefore, the electron correlation plays
a radical role in such materials as high-temperature superconductors and heavy
fermions, etc. To date, there is no agreement on how to deal with higher-order
terms (correlation energy) in the series of electron’s ground state energy
although a method that is termed diagrammatic iteration approach (DIA) was
developed more than one decade ago by the authors of this article. That is why
no consensus on the origin and mechanism of superconductivity has been engaged
in superconductivity community. From the viewpoint of methodology, the DIA is
indeed an approach to higher-order terms from the lower-order ones, i.e. it is a new method to show how to
go beyond the random phase approximation (RPA) step by step by iteration. Here,
we are logically presenting it to the community of modern physics with more analyses
and hope to attract more attention to it and promote its applications.