Singularity in the boundary resistance between superfluid ${}^4$He and a solid surface

Abstract

We report new measurements in four cells of the thermal boundary resistance $R$ between copper and ${}^4$He below but near the superfluid-transition temperature $T_{\lambda }$. For $10^{-7}\le t\equiv 1-T/T_{\lambda }\le 10^{-4}$ fits of $R=R_0{t}^{x_b}+B_0$ to the data yielded $x_b\simeq 0.18$, whereas a fit to theoretical values based on the renormalization-group theory yielded $x_b=0.23$. Alternatively, a good fit of the theory to the data could be obtained if the {\it amplitude} of the prediction was reduced by a factor close to two. The results raise the question whether the boundary conditions used in the theory should be modified.

4 pages, 4 figures, revtex