Universal behavior of3He-4He mixture films near the Kosterlitz-Thouless transition

Abstract

We report measurements of the convective thermal conductance of3He-4He mixture films near the Kosterlitz-Thouless transition. The thickness of our4He films is 14.7 and 19.1 A above the inert layer and the3He concentration ranged from 0.033 to almost 2%. The thermal response is tested for the critical behavior as observed in pure films, and it is found to be preserved in the mixture films case. However, the parametersb, D/a2 andTc exhibit a strong dependence on the concentration. The mixture film conductance at fixedT-Tc is found to decrease upon addition of3He implying a decrease in the 2D correlation length. Mixture films thus exhibit 2D behavior over a narrower temperature range than pure films. Further, for temperaturesT<Tc, the largest measurable conductance decreases sharply with the addition of3He. We attribute this behavior to a3He-4He scattering mechanism and a3He induced free-vortex density.