J. Phys. IV France 12 (2002) Pr9-197
Coexistence of superconductivity and spin density wave orderings in Bechgaard and Fabre saltsC. Pasquier1, P. Auban-Senzier1, T. Vuletic2, S. Tomic2, M. Heritier1 and D. Jerome1
1 Laboratoire de Physique des Solides, bâtiment 510, Centre Universitaire, 91405 Orsay cedex, France
2 Institut za Fiziku, PP. 304, 10001 Zagreb, Croatia
In a small range of pressure, superconductivity (SC) and Spin Density Wave (SDW) states are shown to coexist in the Bechgaard salt (TMTSF) 2PF 6 and the Fabre salt (TMTTF) 2BF 4. In (TMTSF) 2PF 6, a precise investigation of the (P,T) phase diagram has led us to demonstrate the coexistence of the two phases with a superconducting critical temperature which is pressure independent while the critical current at zero field is strongly depressed as the pressure is decreased. In (TMTTF) 2BF 4, using non-linear transport measurements, we present the signature of the presence of 1D superconducting filaments in a small range of pressure. We also investigate the compound under a magnetic field applied along the c *-axis: the upper critical field is more or less pressure independent and is about 2 Tesla (at zero temperature). We suggest that such a high critical field is compatible with the penetration of the magnetic field in the insulating regions of the compound in a similar way of Josephson vortices in layered superconductors.
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