Uniaxial Strain Effects on Transport Properties of a Supramolecular Organic Conductor θ-(DIETS)₂[Au(CN)₄]

Pressure-controlled switching between an insulating state and a superconducting state has been successfully realized on a supramolecular organic conductor theta-(DIETS)(2)[Au(CN)(4)] [DIETS = diiodo(ethylenedithio)diselenadithiafulvalene]. Strong contact between iodine on the donor (DIETS) molecule and nitrogen on the anion [Au(CN)(4)] genetates characteristic uniaxial strain effects on transport properties. Under the ambient pressure, the present system undergoes a semiconductor-insulator transition at 226 K. The effect of strains parallel to the conduction plane (ab-plane) is very small. Even under uniaxial strains up to 20kbar along the a- and b-axis directions, the transition is not suppressed. Surprisingly, however, the c-axis strain induces a superconducting state with T-c of 8.6 K at 10 kbar. Band parameter calculation and the conductivity anisotropy ratio suggest that an increase in the bandwidth W associated with a c-axis strain transforms the system to the metallic and superconducting states. In the metallic state under c-axis strain, the temperature (T) dependence of the Hall coefficient (RH) and the Hall angle (theta(H)) is expressed as R-H proportional to T-1 and cottheta(H) proportional to T-2.