Quantum Hamilton-Jacobi Equation and Broken Symmetry in Hydrodynamics of   Liquid Helium II
  Based on the quantum theory of Bohm and the phase coherence along with the mean field of Penrose and Onsager, it is shown that a free surface of He II behaves like a classical fluid. The broken symmetry of a macroscopic Bose system at the free surface in an external field is discussed in terms of the quantum fluctuations-dissipation. First, we apply this peculiarly universal behavior to explain a breakdown of superfluidity at a vortex core. Secondly, we resolve a long standing puzzle with Landau's two-fluid model on a free surface of a rotating He II in a gravitational field. 
S. J. Han