Unconventional spin density waves in quasi-one dimensional systems

We consider the possibility of formation of an unconventional spin density wave (SDW) in quasi-one dimensional electronic systems. In analogy with unconventional superconductivity, we develop a mean held theory of SDW allowing for the momentum dependent gap Delta(k) on the Fermi surface. The excitation spectrum and basic thermodynamic properties of the model are found to be very similar to those of d-wave superconductors in spite of the different topology of their Fermi surfaces. Among the transport properties the frequency dependent conductivity in directions perpendicular to the linear chain direction is evaluated for various gap functions, and found to reflect the maximum gap value.