Commensurate-incommensurate transition in SDW states of quasi-one-dimensional organic conductors

Spin density wave (SDW) state of a quasi-one-dimensional organic conductors near the quarter-filling has been examined in the presence of dimerization , which leads to properties of half-filling. By applying a transfer integra l method to a single chain with molecular fields determined self consistent ly, it has been shown that two kinds of commensurate states appear for a sm all misfit parameter due to a competition between the commensurability ener gy and the dimerization energy. Several phase diagrams of the commensurate state and the incommensurate state have been obtained as the function of mi sfit parameter, temperature and dimerization.