Possible Existence of Dense Superfluid He-He Mixture in Aerogel.

While studying superfluid He of 2.4 MPa in 97.5 %-porosity aerogel with NMR/MRI techniques, we find that the T is reduced when more than adequate amount of He, which covers the surface of silica strands, is introduced. For a sample, whose T is reduced to as low as 0.9 mK, we find that the spin diffusion coefficient in the normal phase is increased by a factor of 1.56 both in high temperature region, where He-He scattering dominates, and in low temperature region, where He-aerogel scattering dominates. This enhancement is attributed to a modification of Landau parameter $F_{0}^{a}$ from −0.757 to −0.62, which is a change towards less ferromagnetic direction. The modification of microscopic quantity could be explained if small amount of He has homogeneously mixed into liquid He in the aerogel. [ABSTRACT FROM AUTHOR]