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 1 A 1 +, 1 B 1 + and 1 B 2 − states suggest that the 1 A 1 + and 1 B 1 + states are degenerate in the SDW region while the 1 A 1 + and 1 B 2 − states are degenerate in the CDW region. The 1 B 1 + and 1 B 2 − 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.