Thermally driven josephson oscillations in superfluid 4He

We find that a temperature differential can drive superfluid oscillations in 4He. The oscillations are excited by a heater which causes a time dependent temperature differential across an array of 70 nm apertures. By measuring the oscillation frequency and simultaneously determining both temperature and pressure differentials we prove the validity of the most general form of the Josephson frequency relation. These observations were made near saturated vapor pressure, within a few mK of the superfluid transition temperature.     

Statistical mechanics of dilute mixtures of 3He in superfluid 4He

A statistical mechanical theory of the dilute mixtures of ³He and ⁴He is presented. It is shown that the ground state energy is proportional to the ³He density. The chemical potential expressed in terms of the sound velocity assumes the form which has been suggested phenomenologically. From the chemical potential, the effective ³He⁴He interaction and osmotic pressure are derived. The effective mass of ³He is also calculated as a function of potential parameters.