Microwave attenuation in CuO superconducting powders

We give an explanation in terms of k = 0 mode response of the observed magnetic field dependence of the microwave absorption ΔP(H) = P(H)-P(0) seen in recent experiments on powdered samples of YbCo. A uniform magnetic field in a (flavor) singlet representation of a superconductor (SDW) induces a modulation at wave number QHα√H corresponding to weak pinning. The field dependence ΔP(H)/Q2H = ∂ left angle h2 right angle /∂lnQ2, left angle h2 right angle ∝ ln(Q2 + Q2H) in agreement with experiment, Q being the wave number of the thermal shear. (orig.)