Singlet Superfluidity in<sup>3</sup>He Film on<sup>4</sup>He Film
Abstract
It is predicted that spin-singlet superfluidity can be realized in a submonolayer 3 He film on the surface of thin film of superfluid 4 He. The basic mechanism of the superfluidity is the attraction between 3 He quasi particles arising from exchange of virtual third sound quanta. It is argued that the superfluid transition of 3 He film is of Kosterlitz-Thouless nature if the 4 He film is thick, and changes its nature as the 4 He thickness is reduced, with a crossover thickness of ∼2 atomic layers. Several experiments are suggested to detect the new phase transition, to test whether the proposed mechanism is really working, and to exanaine the nature of the transition. The transition temperature is estimated to be in a temperature range attainable with a dilution refrigerator.