Singlet/triplet transition in a two-band organic superconductor

Abstract: We study quasi-one-dimensional organic superconductors with two-band dispersion. We use spin ladder approximation with the Hubbard model. We determine the symmetry of the Cooper pairing by calculating the free energy. Thanks to close values of singlet and triplet scatterings, the phase diagram reveals that, at high magnetic field, the triplet configuration is more favorable, indicating a transition from singlet superconducting state at low fields to triplet one. This result confirms similar ones in one-band system and can explain recent experimental results on (TMTSF)2ClO4. [Copyright &y& Elsevier]