Evidence for two superfluid transitions inHe3-He4films

Abstract

Two superfluid phase transitions in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films have been observed. Both transitions, $A$ and $B$, possess Kosterlitz-Thouless characteristics, but phase $B$ has a much less pronounced onset signal. At constant ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ coverage the transition temperature of $A$ decreases while that of $B$ increases upon addition of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. We discuss possible interpretations of these results based on existing theories and connections with other measurements.