Viscosity of liquid He-4 and quantum of circulation: Why and how are they related?

Original · EN

The relationship between the apparently unrelated physical quantities -- kinematic viscosity of liquid He-4, ν, and quantum of circulation, κ=2πℏ/m₄, where ℏ is the Planck constant and m₄ denotes the mass of the ⁴He atom -- is examined in the vicinity of the superfluid transition occurring due to Bose-Einstein condensation. A model is developed, leading to the surprisingly simple relation ν≈ κ/6. We critically examine the available experimental data for ⁴He relevant to this simple relation and predict the kinematic viscosity for the stretched liquid ⁴He along the λ-line at negative pressures.