Superconductivity and metal-insulator transitions in (TMTSF)₂X

The family of organic conductors (TMTSF)2X exhibits a variety of metal-insulator transitions which compete with superconductivity. We report on thermodynamic, transport and superconducting measurements which determine the electronic dimensionality. We discuss the magnetic field induced "transition" in the low temperature properties and suggest that it may result from the cross-over to the extreme quantum limit for the least conducting direction. We also discuss the possible coexistence of superconducting and spin density wave states. We demonstrate the inconsistency of proposed high temperature superconducting fluctuations with a wide body of experimental evidence. © 1983.