Elementary Defects, Halfons, Connecting the SDW and CDW in the One Dimensional Extended Hubbard Model

Abstract

We show in the Hartree-Fock approximation that electronic defects which are SDW-CDW domain walls exist in the one dimensional extended Hubbard model of half filling. In the vicinity of the SDW-CDW phase boundary, SDW and CDW polarons and charged solitons split into confined pairs of these defects. They become freely mobile along a chain on the phase boundary. They have ±1/4 spins and ±1/2 charges in an equidistant lattice and are called halfons. Halfon pairs can convert smoothly the SDW and CDW and can be major quantum fluctuations in the SDW-CDW phase transition. In a bond alternated lattice their spins and charges, respectively, deviate from 1/4 and 1/2. On the SDW-CDW phase boundary, there exist new density waves called the mixed density waves (MDW). Halfons are classified by their trajectories connecting the SDW and CDW via the MDW. We derive the counting rules to explain their fractional spins and charges.