Uniaxial Strain Effects on Transport Properties of a Supramolecular Organic Conductor θ-(DIETS)_2[Au(CN)_4] (Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties)

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Pressure-controlled switching between an insulating state and a superconducting state has been successfully realized on a supramolecular organic conductor θ-(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 20 kbar 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 (R_H) and the Hall angle (θ_H) is expressed as R_H α T^<-1> and cotθ_H α T^2.
社団法人日本物理学会の論文
2003-05-15