DOI: 10.1051/jp1:1994162
J. Phys. I France 4 (1994) 579-594

Field and frequency dependent transport in the two-dimensional organic conductor -(BEDT-TTF) ₂I ₃

M. Dressel¹, G. Grüner¹, J.P. Pouget², A. Breining³ and D. Schweitzer<sup>3

1</sup>  Department of Physics and Solid State Science Center, University of California, Los Angeles, CA 90024-1547, U.S.A.
²  Laboratoire de Physique des Solides, Universite Paris-Sud, F-91405 Orsay, France
³  Drittes Physikalisches Institut, Universit5.t Stuttgart, D-70569 Stuttgart, Germany

(Received 10 October 1993, accepted in final form 3 January 1994)

Abstract
The title compound undergoes a metal-insulator phase transition of unknown origin at T _MI = 135 K. We studied the electrodynamic response of -(BEDT-TTF) ₂I ₃ in a avide range of frequency, covering microwave and millimeter wave frequencies as well as the optical spectral range, and found a frequency dependent conductivity up to 1000 cm ^-1 in the low temperature phase. This is accompanied be a non-linear transport with a smooth onset at about 10 V/cm. Our X-ray studies show no indication of superstructure reflections and clearly rule out the formation of a charge density wave ground state. The lack of a temperature dependence in the millimeter wave conductivity between 20 K and 100 K makes hopping transport unlikely.

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