Possible Spin-Singlet Superconductivity in (TMTSF)₂X: Superconducting Transition Temperature in a Magnetic Field

Abstract

We study the transition temperature T_c(H) of a quasi-one-dimensional (Q1D) superconductivity which is derived from the quantum effect of electron motion in a strong magnetic field. We calculate T_c(H) of both isotropic and anisotropic superconductivity by taking account of the optimal momentum of the Cooper pairs and the effect of higher harmonic terms along the second conducting axis in the tight-binding model. We find that, although T_c(H) of the spin-singlet superconductivity is strongly suppressed by the Zeeman effect, the suppression of T_c(H) is not very severe if we take the optimal pair-momentum and the higher harmonic terms into account. The obtained T_c(H) for the spin-singlet superconductivity is consistent with the experimental results in TMTSF salts.