Simultaneous competition and coexistence between charge-density waves and reentrant superconductivity in the pressure-temperature phase diagram of the molecular conductor TTF [Ni(dmit)2]2 (TTF is tetrathiafulvalene and dmit is the 1,3-dithia-2-thione-4,5-dithiolato group)

Abstract

The pressure-temperature phase diagram of the quasi-one-dimensional molecular superconductor TTF [Ni(dmit)2]2 has been carefully determined by ac resistivity measurements up to 14 kbar. Increasing pressures induce electronic phase transitions between a high-temperature metal and successive, metallic or semimetallic, semiconducting and reentrant superconducting ground states. This unusual phase diagram is compared with that of TTF [Pd(dmit)2]2. It is discussed in connection with ambient-pressure charge-density-wave (CDW) instabilities, the wave vector of which can be well accounted for by an original conduction-band structure involving both the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals of the acceptor slabs. It is confirmed that the superconducting temperature increases slowly with increasing pressure. It is suggested that the superconductivity coexists with a high-temperature CDW instability and is in weak competition with low-temperature CDW fluctuations; these CDW’s affect different parts of the Fermi surface.

Source-reported materials — not catalogue approval

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