Superconductivity in the family of organic salts based on the tetramethyltetraselenafulvalene (TMTSF) molecule: (TMTSF)2X (X=ClO4, PF6, AsF6, SbF6, TaF6)

Abstract
The authors report resistivity measurements along the high-conductivity axis of (TMTSF)2ClO4, (TMTSF)2TaF6 and (TMTSF)2SbF6 for various hydrostatic pressures up to 12.5 kbar, and for transverse magnetic fields of up to 50 kG, in the temperature range 100 mK-4K. These measurements show that all three compounds have a superconducting phase transition near 1K when sufficient pressure is applied (TMTSF)2SbF6 and (TMTSF)2TaF6 become superconducting for pressures above 10 kbar and 11 kbar respectively. At lower pressures a metal-insulator phase transition is observed which is probably associated with a spin density wave (SDW) instability. They observe a superconducting phase transition in (TMTSF)2ClO4 at much lower pressures (2X salts.