Quantum fluctuations in the one dimensional hubbard model with a less than half filling

Summary form only given. The electronic structure of the one dimensional Hubbard model with a less than half filling is studied by the resonating Hartree-Fock (Res HF) method. As basic units of quantum fluctuations in the ground state of the model, we consider charged and neutral solitons (S/sup +/ and S/sup 0/) and polarons (P/sup +/) in the spin density wave (SDW). The HF ground state of the system is an S/sup +/ gas at small U´s and is a P/sup +/ gas at large U´s, where U is the on-site Coulomb repulsion. The defects make a lattice in the weak correlation and large defect density regime, while they can move almost freely in the strong correlation and small defect density regime. In the real ground state these defects perform quantum translational and breathing motions and convert each other via the process S/sup +/ + S/sup 0/ - P/sup +/. Employing this picture of quantum fluctuations, the Res HF wave function composed of only 6 Slater determinants can explain at most 98.6% (U/t = 2) and at least 82.2% (U/t = 8) of the exact correlation energy in the Hubbard ring with 16 sites and 14 electrons, where t is the transfer energy.