Equal-spin-pairing superfluid phase ofHe3in an aerogel acting as an impurity

Abstract

The superfluid phases of $^{3}\mathrm{He}$ in a 97.5% porosity aerogel have been studied using cw and pulsed NMR techniques at several pressures. The equilibrium equal-spin-paring superfluid phase, $A$-like phase region is observed very near ${T}_{c}^{\phantom{\rule{0.1em}{0ex}}\mathit{aero}}$, and that region normalized with ${T}_{c}^{\phantom{\rule{0.1em}{0ex}}\mathit{aero}}$ is found to be independent of pressure in contrast with that of the bulk $A$ phase. Tipping angle dependent frequencies in the free induction decay signal of the $A$-like phase are quite different from those of the bulk $A$ phase. On these grounds, we propose that the $A$-like phase in aerogel is a different superfluid phase and can be described as a robust state introduced by Fomin [JETP Lett. 77, 240 (2003)].