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 measurements under pressure. Superconductivity is reported for the first time in (TMTTF) 2 BF 4 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.