Electronic structure of the Hubbard and extended Hubbard models: An exact diagonalization study

Abstract

An exact diagonalization technique for small clusters is used to study the electronic structure of the Hubbard model with nearest-neighbor repulsive interaction. The phase diagram of the model is extracted from the calculated charge and spin correlation functions and single-particle excitation spectra. It is shown that the small Fermi surface is realized in a parameter and doping region, which may provide a complementary understanding of the large Fermi surface believed to exist in the Hubbard model.