Critical Surface Density of the Superfluid Component inHe4Films

Abstract

It is shown that published third-sound measurements are in very good agreement with the theoretical result by Nelson and Kosterlitz that in the limit as $T\to {T_c}^{-}$ the ratio of the density per unit area of superfluid component to the critical temperature, $T_c$, is the universal constant $\left(\frac{2}{\pi }\right){\left(\frac{m}{\hslash }\right)}^2{k}_{\mathrm{B}}$.