Thermodynamics and optical conductivity of unconventional spin density waves

We consider the possibility of formation of an unconventional spin density wave (USDW) in quasi-one-dimensional electronic systems. In analogy with un conventional superconductivity, we develop a mean field theory of SDW allow ing for the momentum dependent gap Delta (k) on the Fermi surface. Conditio ns for the appearance of such a low temperature phase are investigated. The excitation spectrum and basic thermodynamic properties of the model axe fo und to be very similar to those of d-wave superconductors in spite of the d ifferent topology of their Fermi surfaces. Several correlation functions ar e calculated, and the frequency dependent conductivity is evaluated for var ious gap functions. The latter is found to reflect the maximum gap value, h owever with no sharp onset for absorbtion.