Strongcoupling approach for strongly correlated electron systems
Abstract
A perturbation theory scheme in terms of electron hopping, which is based on the Wick theorem for Hubbard operators, is developed. Diagrammatic series contain singlesite vertices connected by hopping lines and it is shown that for each vertex the problem splits into the subspaces with ``vacuum states'' determined by the diagonal Hubbard operators and only excitations around these vacuum states are allowed. The rules to construct diagrams are proposed. In the limit of infinite spatial dimensions the total auxiliary singlesite problem exactly splits into subspaces that allows to build an analytical thermodynamically consistent approach for a Hubbard model. Some analytical results are given for the simple approximations when the twopole (alloyanalogy solution) and fourpole (HartreeFock approximation) structure for Green's function is obtained. Two poles describe contribution from the Fermiliquid component, which is dominant for small electron and hole concentrations (``overdoped case'' of highT_{c}'s), whereas other two describe contribution from the nonFermi liquid and are dominant close to halffilling (``underdoped case'').
 Publication:

Physical Review B
 Pub Date:
 July 2000
 DOI:
 10.1103/PhysRevB.62.2358
 arXiv:
 arXiv:condmat/9911255
 Bibcode:
 2000PhRvB..62.2358S
 Keywords:

 71.10.Fd;
 71.15.Mb;
 05.30.Fk;
 71.27.+a;
 Lattice fermion models;
 Density functional theory local density approximation gradient and other corrections;
 Fermion systems and electron gas;
 Strongly correlated electron systems;
 heavy fermions;
 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 14 pages, revtex, feynmf, 5 EPS figures, twocolumn PRB style, published in PRB