Possible Existence of Dense Superfluid 3He-4He Mixture in Aerogel

Abstract

While studying superfluid 3He of 2.4 MPa in 97.5 %-porosity aerogel with NMR/MRI techniques, we find that the TC is reduced when more than adequate amount of 4He, which covers the surface of silica strands, is introduced. For a sample, whose TC 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 3He-3He scattering dominates, and in low temperature region, where 3He-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 4He has homogeneously mixed into liquid 3He in the aerogel.