Theory of Thermal Conductivity inYBa2Cu3O7−δ

We calculate the electronic thermal conductivity in a d-wave superconductor, including both the effect of impurity scattering and inelastic scattering by antiferromagnetic spin fluctuations. We argue that phonons dominate heat transport near $T_c$, but that electrons are responsible for most of the peak observed in clean samples, The peak position is predicted to vary nonmonotonically with disorder, in good agreement with experiments on ${\mathrm{YBa}}_2({\mathrm{Cu}}_{1-x}{\mathrm{Zn}}_x{)}_3{\mathrm{O}}_{7-\delta }$.