J. Phys. IV France 12 (2002) Pr9-201
Charge ordering in non-dimerized BEDT-TTF based organic conductors: 13C-NMR experimentsT. Takahashi1, R. Chiba1, Y. Takano1, Y. Kubo1, K. Hiraki1, H. Yamamoto2 and T. Nakamura3
1 Gakushuin University, Mejiro 1-5-1, Toshima-ku, Tokyo 171-8588, Japan
2 RIKEN, The Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198, Japan
3 Institute for Molecular Science, Saigo-naka 38, Myodaiji-cho, Okazaki 444-8585, Japan
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, a-I, and 8-RbZn(SCN) 4, the formation of charge stripes perpendicular to molecular stacks are confiied. Charge disproportionation is estimated as 0.8:0.2 in the latter and more in the former. It is also observed that charge disproportionation already develops well above the MI transition temperature while no long-range charge order is stabilized. This seems to require a serious reconsideration of the transport properties in the `metallic' state.
© EDP Sciences 2002