Selectively deuterated molecular conductor (DMe-DCNQI)2Cu —phase diagram and dimensionality—

The mixed-valence Cu salt of the π—acceptor DMe-DCNQI exhibits a unique pressure-temperature phase diagram. We present fine tuning of the effective pressure (0–500 bar) by selective deuteration of the DMe-DCNQI molecule. Especially, the selective deuteration at the methyl group(s) has made it possible to observe the giant metal-insulator-metal (reentrant) transition at ambient pressure. The 13C-substitution at the cyano groups also positively shifts the effective pressure by ca 100 bar. In all these isotope effects, the coordination around the Cu ion is considered to play an important role. A simple tight-binding band calculation indicates that the hybridization between the organic pπ band and 3d orbital provides the three-dimensional Fermi surface, which well explains the result of the de-Haas van Alphen effect measurement.