J. Phys. IV France
Volume 114, April 2004
Page(s) 263 - 267

J. Phys. IV France
114 (2004) 263
DOI: 10.1051/jp4:2004114055

Pressure control of transport property of organic conductors; $\alpha$-, $\theta $-(BEDT-TTF) 2I 3 and $\theta $ -(DIETS) 2[ Au(CN) 4]

N. Tajima1, A. Tajima1, M. Tamura1, R. Kato1, Y. Nishio2 and K. Kajita2

1  RIKEN, JST-CREST, Hirosawa 2-1, Wako, Saitama 351-0198, Japan
2  Department of Physics, Toho Univ., Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan

Transport properties of three organic systems, $\alpha$ -(BEDT-TTF) 2I 3, $\theta $-(BEDT-TTF) 2I 3 and $\theta $ -(DIETS) 2[ Au(CN) 4] , as controlled by hydrostatic pressure or uniaxial strain, are overviewed. We found interconversion between a narrow-gap semiconductor and a metal both in two types of (BEDT-TTF) 2I 3 salts. By application of uniaxial strain along the b-axis, the narrow-gap semiconductor state, found in $\alpha$ -(BEDT-TTF) 2I 3 under hydrostatic pressure, is transformed into a metallic state similar to that in $\theta $-(BEDT-TTF) 2I 3 under ambient pressure. On the other hand, $\theta $-(BEDT-TTF) 2I 3 undergoes a transition to a narrow-gap semiconductor state by application of hydrostatic pressure of about 5 kbar. For $\theta $ -(DIETS) 2[ Au(CN) 4] , stabilization of metallic state, accompanied by superconductivity, is observed only when a uniaxial strain perpendicular to the conduction layers is applied. This peculiar behavior is attributable to the unconventional supramolecular architecture of this material. Key words. Narrow-gap semiconductor, superconductor, uniaxial strain, Hall effect, carrier density, mobility.

© EDP Sciences 2004