13C-NMR studies of charge ordering in organic conductors

Experimental evidences of the charge ordering with the use of 13C-NMR techniques in various organic conductors are reviewed. In the insulating states of two-dimensional BEDT-TTF salts, α-I3 and θ-RbZn(SCN)4, the formation of charge stripes perpendicular to molecular stacks are confirmed. Charge disproportionation is estimated as 0.8:0.2 in the latter and more in the former. New type of charge ordering in a TTM-TTP salt with one-dimensional half-filled band is suggested.