Electronic dynamic Hubbard model: Exact diagonalization study
Abstract
A model to describe electronic correlations in energy bands is considered. The model is a generalization of the conventional Hubbard model that allows for the fact that the wave function for two electrons occupying the same Wannier orbital is different from the product of singleelectron wave functions. We diagonalize the Hamiltonian exactly on a foursite cluster and study its properties as a function of band filling. The quasiparticle weight is found to decrease and the quasiparticle effective mass to increase as the electronic band filling increases, and spectral weight in one and twoparticle spectral functions is transferred from low to high frequencies as the band filling increases. Quasiparticles at the Fermi energy are found to be more “dressed” when the Fermi level is in the upper half of the band (hole carriers) than when it is in the lower half of the band (electron carriers). The effective interaction between carriers is found to be strongly dependent on band filling becoming less repulsive as the band filling increases and attractive near the top of the band in certain parameter ranges. The effective interaction is most attractive when the singlehole carriers are most heavily dressed, and in the parameter regime where the effective interaction is attractive, hole carriers are found to “undress,” hence become more like electrons, when they pair. It is proposed that these are generic properties of electronic energy bands in solids that reflect a fundamental electronhole asymmetry of condensed matter. The relation of these results to the understanding of superconductivity in solids is discussed.
 Publication:

Physical Review B
 Pub Date:
 January 2003
 DOI:
 10.1103/PhysRevB.67.035103
 arXiv:
 arXiv:condmat/0207369
 Bibcode:
 2003PhRvB..67c5103H
 Keywords:

 71.10.Fd;
 74.20.Mn;
 Lattice fermion models;
 Nonconventional mechanisms;
 Condensed Matter  Strongly Correlated Electrons;
 Condensed Matter  Superconductivity
 EPrint:
 Small changes following referee's comments