The SDW-CDW phase transition and quantum fluctuations in the one dimensional extended Hubbard model

We study the natures of the SDW-CDW phase transition and quantum fluctuations in the one dimensional extended Hubbard model using the resonating Hartree-Fock method. The size dependences of the energies of the lowest 1A1+, 1B1+ and 1B2− states suggest that the 1A1+ and 1B1+ states are degenerate in the SDW region while the 1A1+ and 1B2− states are degenerate in the CDW region. The 1B1+ and 1B2− states cross at the phase boundary. We show that the dominant quantum fluctuations near the phase boundary are the SDW-CDW domain walls called halfons.