Superconductivity and spin-density waves: organic superconductors

Abstract

When superconductivity coexists with a spin-density wave (SDW) for the same electrons, both spin-singlet and spin-triplet Cooper-pair amplitudes of comparable magnitude must occur. Physical properties of the coexistence states are strongly affected by the amplitude of spin-triplet Cooper pairs even when the electron-electron interaction for triplet pairing, and hence the triplet pair potential, are both zero. The coexistence phase may occur in (TMTSF)2X organic superconductors where SDW and superconductivity phases meet on the temperature-pressure phase diagram. Compared with the superconductivity-only phase, the SDW superconductivity coexistence state is predicted to have a higher Pauli-limited critical magnetic field and a reduced sensitivity of the transition temperature to non-magnetic impurities.