Magnetic properties of organic two-leg spin–ladder systems with S=1/2 and S=1 Original Research Article

Competition between p-, d-, and f-wave pairings in the organic superconductor (TMTSF)2X is discussed, where the major ingredients are: (i) quasi-one-dimensionality, (ii) coexistence of charge and spin fluctuations, and (iii) anisotropy in the spin fluctuation in this material. We then propose that the pairing symmetry can be experimentally identified from the tunneling spectroscopy, where the p-, d-, f-waves should exhibit a U-shaped gap+a zero-energy peak, V-gap, or V+zero-energy peak, respectively.