Quantum cavitation: a comparison between superfluid helium-4 and normal liquid helium-3

Cavitation has now been studied in superfluid helium-4 and in normal liquid helium-3, both theoretically and experimentally. We compare the two cases and discuss the existence of a crossover from quantum cavitation, where bubbles are nucleated by tunneling, to classical cavitation where their nucleation is thermally activated. In helium-3, where evidence for quantum nucleation is lacking, the interpretation of the experimental results leads to two related questions. The first one concerns the extrapolation of the properties of this Fermi liquid at negative pressure. The second one concerns the validity of present theories of quantum cavitation in a Fermi liquid.