Possibility of Coexistence of Spin Density Wave and Superconductivity in Organic Conductor (TMTSF)2PF6

A theory for the coexistence problem of the spin density wave (SDW) and superconductivity (SC) in highly anisotropic materials is presented. On the basis of a simplified electronic band model a Hartree-Fock approximation is applied. It is concluded that SDW is precluded when SC developes at a higher temperature. When the SDW onset temperature is higher than that of SC, these long range orders generally coexist unless two orders interchange by a first order phase transition. Discussions on possible phase diagrams for (TMTSF)₂PF₆ under pressure are given.