Metastability and superfluid fraction of the A-like and B phases of $^3$He in aerogel in zero magnetic field

We report the low frequency sound measurements of the metastable A-like (A$^\ast$) phase of superfluid $^3$He confined within a 98% open aerogel matrix in zero magnetic field. The second sound-like (slow) mode provides an accurate determination of the superfluid fraction of (and the transition between) the A$^\ast$ and B phases. The A$^\ast$ and B phases exhibit stable coexistence in the presence of disorder, the ratio of their superfluid fractions, $\rho_{s}^{A^\ast}/\rho_s^B$, is much smaller than that of the bulk A and B phases, and argues that the A$^\ast$ and bulk A phases are distinct.