Antiparamagnons and the thermal conductivity of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

We calculate the electronic contribution to the thermal conductivity and find a peak below ${\mathit{T}}_{\mathit{c}}$ in agreement with experiment. In our model, the quasiparticle damping is due to inelastic scattering from antiparamagnons. Our results support the recent conjecture by Yu et al. that some sort of suppression of quasiparticle damping is responsible for this peak. The correlation between these measurements, the microwave conductivity, and many others strongly supports the view that antiferromagnetic spin fluctuations in the ${\mathrm{CuO}}_2$ planes dominate the quasiparticle lifetime.