J. Phys. IV France 12 (2002) Pr9-201
DOI: 10.1051/jp4:20020395

Charge ordering in non-dimerized BEDT-TTF based organic conductors: ¹³C-NMR experiments

T. Takahashi¹, R. Chiba¹, Y. Takano¹, Y. Kubo¹, K. Hiraki¹, H. Yamamoto² and T. Nakamura<sup>3

1</sup>  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

Abstract
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