Nonlinear Conductivity in Dicyanoquinonediimine Complexes

概要

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Nonlinear conductivity is observed below the metal–insulator (M–I) transitions of molecular conductors, halogen-substituted ($R_{1}$,$R_{2}$-DCNQI)2Cu (DCNQI: dicyanoquinonediimine, $R_{1}$,$R_{2}$: methyl or halogen). Despite the difference of the M–I transition temperatures depending on the halogens, these compounds show nonlinear properties at similar low temperatures (${<}80$ K), and the characteristics are regarded as “activation” type. The complex of deuterated dimethyl-DCNQI ($d_{2}$-DMeDCNQI)2Cu, which shows reentrant M–I–M transitions, exhibits irreversible switching from a low-conducting state to a high-conducting state in the intermediate I state. Since the Peierls distortion is irreversibly erased by the electric field, this phenomenon is called “Peierls memory”. In addition, “inverse” nonlinear conductivity from a high-conducting state to a low-conducting state is observed at the low-temperature M state, which is not only entirely reversible but also accompanied by a new kind of rapid current oscillation in the order of 3 kHz. These observations demonstrate metastable nature of the intermediate I state.
2010-09-15