Pressure control of transport property of organic conductors; α-, θ-(BEDT-TTF)2I3and θ -(DIETS)2[ Au(CN)4

Abstract

Transport properties of three organic systems, α-(BEDT-TTF) 2 I 3 , θ-(BEDT-TTF) 2 I 3 and θ-(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) 2 I 3 salts. By application of uniaxial strain along the b-axis, the narrow-gap semiconductor state, found in α-(BEDT-TTF) 2 I 3 under hydrostatic pressure, is transformed into a metallic state similar to that in θ-(BEDT-TTF) 2 I 3 under ambient pressure. On the other hand, θ-(BEDT-TTF) 2 I 3 undergoes a transition to a narrow-gap semiconductor state by application of hydrostatic pressure of about 5 kbar. For θ-(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.