HALFON EXCITATIONS CONNECTING SDW AND CDW

The 1/2 filled extended Hubbard model has a SDW and a CDW as the HF gr ound states. On the SDW-CDW phase boundary, a polaron and a charged so liton in the SDW and CDW split into a pair of new topological defects, halfons. A halfon is a defect that is a boundary connecting SDW and C DW. It has +/-1/4 spin and +/-1/2 charge in an equidistant chain. The SDW and CDW can be mutually converted via halfon pairs. In a bond alte rnated chain, the halfons are divided into two groups, the magnitudes of spin and charge become smaller than 1/4 and 1/2 in a group but beco me larger in another group. We develop a systematic classification of the halfons in terms of their phase variable trajectories via new dens ity wave states. We show that there are 16 distinct halfons and give t he counting rules of their spins and charges.