Phenomenological Theory of Collisionless SuperfluidHe3

Abstract

According to a phenomenological theory of collisionless superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, the velocity of high-frequency sound should show a transition from zero- to first-sound velocities as the superfluid fraction $\frac{{\rho }_s}{\rho }$ is increased. From the experimental observations of this behavior by Paulson, Johnson, and Wheatley, the order parameter $\frac{{\rho }_s}{\rho }$ can be determined for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ II.