Unusual Critical Field Behavior in (TMTSF)_2X
Abstract
Upper critical magnetic field phase diagrams have been determined along the three principal directions in the X=ClO4 and X=PF6 superconductors with high angular precision. In the ClO4 salt, we have previously shown that strong upward curvature is present in H_c2(T) for field aligned along the intermediate b direction.(I.J. Lee, et al., Synth.Met.70,747(1995); Appl.Superc.2,753(1995).) We present here new results on the PF6 system under pressure, via resistivity measurements. Near T_c=1.13K, the critical fields and their slopes are in the ratio H_a>H_b>H_c, as expected for these quasi-1D systems. However, an anisotropy crossover occurs near T/T_c=0.7, below which the critical field along b exceeds that along a. The resulting phase diagram is similar to that seen in UPt_3. In addition, H_c2(T) along b displays positive curvature at all fields and temperatures, with no sign of saturation to our highest and lowest (0.06K and 7T). We discuss these results in light of recent theories on superconductivity in high magnetic fields.(A.G. Lebed, JETP Lett. 44, 114 (1986); M. Rasolt and Z. Tesanovic, Rev. Mod. Phys. 64, 709 (1992); N. Dupuis, G. Montambaux and C. Sa de Melo, Phys. Rev. Lett. 70, 2613 (1993).)
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1996
- Bibcode:
- 1996APS..MAR.A1207L