From Mott insulator to superconductivity in (TMTTF)2BF4:: high pressure transport measurements

Within the generic (pressure, temperature) phase diagram of (TM)(2)X compounds, we have investigated the crossover between the spin density wave and superconducting ground states by transport measurement's under pressure. Superconductivity is reported for the first time in (TMTTF)(2)BF4 below 1.38 K, in the pressure range 33.5-37.5 kbar, and coexists with the spin density wave phase, present alone at lower pressure. Differential resistance measurements support the idea of a phase segregation with the proportion of the superconducting phase (related to the measured critical current) increasing with pressure. (C) 2002 Elsevier Science B.V. All rights reserved.