Superconductivity and spin-density waves: organic superconductors

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) 2 X 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.