Singularity in the Kapitza resistance between gold and superfluidHe4nearTλ

We report experimental results for the thermal boundary resistance ${\mathrm{R}}_{\mathrm{K}}$ between gold and superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ which were obtaiend by the use of thermometry with 3-nK resolution. The data imply that ${\mathrm{R}}_{\mathrm{K}}$ is singular at the superfluid transition temperature ${\mathrm{T}}_{\lambda }$. Comparison with theory suggests that the singularity results from a hydrodynamic effect proposed by Landau, and that it is associated with the vanishing of the superfluid and normal-fluid currents at the boundaries.