Superconductivity and spin-density waves

Superconductivity in a metal with a spin-density-wave (SDW) broken symmetry is investigated within the framework of the Bardeen-Cooper-Schrieffer (BCS) theory. The gap equation is solved analytically, leading to a gap that falls to zero at the SDW gap for a spiral SDW, and to a small, but nonzero value, for a linear SDW. The electronic specific heat in the superconducting state acquires a low-temperature tail, far in excess of a BCS exponential falloff. The ultrasonic attenuation exhibits a similar deviation from the usual BCS result.