Evidence for Superfluidity in the Newly Found Phases ofHe3

Abstract

The relative viscosity $\eta$ of liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured along the melting curve from 10 mK to about 1 mK with a vibrating-string viscometer. As the temperature is reduced, $\eta$ first increases as expected until the pressure anomaly "$A$" is reached. The viscosity then starts to decrease, has a discontinuous drop at the pressure anomaly "$B$," and then continues to diminish rapidly. The lowest measured value of $\eta$ is 1000 times smaller than that at point $A$. This must be regarded as strong evidence for superfluidity.