Optical interferometry in superfluid He-3-B

We report interferometric measurements on 0.1...1 mm thick films of super-fluid He-3-B. The menisci of three different rotational states of the superfluid were observed and analyzed theoretically using two-fluid hydrodynamics: These are (i) the equilibrium vortex state in which the superfluid and the normal components corotate (solid body rotation), (ii) the vortex-free state (the Landau state), in which only the normal component rotates, and (iii) the quasistationary vortex state in which only the superfluid fraction rotates (pure superfluid rotation). The Landau state manifested itself by a reduced parabolic meniscus at rotations speeds below the critical angular velocity Omega(c) less than or similar to 0.2 rad/s for vortex formation. Transition from the Landau state to the equilibrium vortex state yielded a sudden deepening of the meniscus when Omega(c) was exceeded. After a rapid halt of the cryostat, we observed a novel meniscus which was produced by th superfluid rotation while the normal component was at rest. The enhanced depth of this meniscus is governed by the reactive and for thermomechanical excitation, we measured the response of a thin superfluid layer to a heat pulse and analyzed it within the theory of two-fluid hydrodynamics. The data were employed, using the dispersion relation for thin film oscillations, to deduce the second viscosity coefficient zeta(3) close to T-c.