Semimetallic SDW State in Quasi One-Dimensional Conductors

Abstract

A quasi one-dimensional Hubbard model embodying features of (TMTSF) 2 PF 6 etc. was studied. The SDW gap equation derived by a variational method is solved. The gap parameter is derived at OK and at finite temperatures as a function of the transverse electron transfer energy t '. The SDW transition proves to be of the second order. The upper and lower bands separated by the SDW gap start to overlap due to finite value of t ' when the gap becomes smaller than the magnitude of modulation of band extrema. The temperature dividing the SDW phase into semiconducting and semimetallic phases is also obtained. Physical properties such as state density, magnetoresistivity, conductivity, susceptibility etc. are briefly described. Experimental observations agree qualitatively well with the above results, if we take t '∼300 k B and assume appropriate pressure dependence of t '.