Unconventional quarter-filled SDW states with alternating potential and dimerization

The interplay of alternating potential and dimerization (u) has been examin ed for the spin density wave (SDW) state in a quasi-one-dimensional system at quarter-filling, which is expressed in terms of theta, a phase of the SD W. By taking account of the dimerization energy u(2) / (2g) with an effecti ve coupling constant g, we evaluate critical temperatures, T-c, T-s and T-u , corresponding to the onset of Delta(c)(proportional to < cos theta >). De lta(s)(proportional to < sin theta >) and u, respectively. Two kinds of not iceable critical temperatures of the SDW states are obtained where T-c > T- s = T-u for g < g(c) and T-u > T-c = T-s for g > g(c). The quantity g(c) is increased by both the alternating potential and the interchain coupling. T he relevance to the SDW state in (EDT-TTF)(2)AuBr2 salt is discussed.