Resonating Hartree-Fock Studies on Electron Correlation and Bond Alternation in the One Dimensional Half Filled Hubbard Model

Abstract

Effects of the on-site electron-electron Coulomb interaction U on bond alternation in the one dimensional half filled Hubbard model are studied by the resonating Hartree-Fock method. Two kinds of SDW neutral solitons S_A⁰ and S_B⁰ exist in a bond alternated lattice which are centered at a long bond and a short bond, respectively. S_A⁰ enhances but S_B⁰ suppresses the alternating bond order (ABO) due to bond alternation. Quantum fluctuations in the ground state involve more S_A⁰’s than S_B⁰’s because the former has lower energy than the latter with increasing bond alternation so that they enhance the ABO in the true ground state and consequently the bond alternation. The spin and singlet pair correlation functions show that electrons tend to make singlet pairs on nearest neighbor short bonds even from small U’s and small bond alternations.