SEARCH FOR NOVEL REENTRANT SUPERCONDUCTIVITY AT HIGH MAGNETIC-FIELD IN A QUASI-ONE-DIMENSIONAL ORGANIC SUPERCONDUCTOR

In recent theoretical works, Lebed' et al., Dupuis and Montambaux, and Tesanovic et al. predict novel upper critical field features in quasi -1-D and quasi-2-D superconductors. In the 1-D case, a Larkin-Ovchinni kov-Fulde-Ferrell (LOFF) state is proposed to occur at high magnetic f ield owing to topological k-space considerations. For the 2-D case, qu antum effects associated with Landau quantization lead to comparable p redictions, which include a type of reentrant superconductivity hither to unexplored. We have reinvestigated the superconducting transition i n a candidate material, (TMTSF)(2)ClO4, which can be regarded as both quasi-1-D and quasi-2-D. The magnetic field was oriented in such a way as to satisfy the requirements of either dimensional effect. At low t emperature, we find both positive curvature and positive slope in H(T) phase space, and discuss here the prospect of these features being re presentative of high field superconductivity.