Spin Density Wave and Superconductivity in Highly Anisotropic Materials. III. Energy Gap Structure and Non-Magnetic Impurity Effects

Abstract

Based on a simple anisotropic electron band model within the Hartree-Fock approximation the coexistence problem of the spin density wave and superconductivity is further investigated theoretically. It is demonstrated that (1) the energy gap structure is quite different from an ordinary superconductor in the coexistent region, and (2) non-magnetic impurities substantially alter the energy gap structure, giving rise to a bound state inside the energy gap and raise the superconducting transition temperature. Discussions on the electron tunneling experiment of (TMTSF)₂PF₆ under pressure are given.