Impurity effects on the A1-A2 splitting of superfluid 3He in aerogel -: art. no. 224502

When liquid He-3 is impregnated into silica aerogel a solid-like layer of He-3 atoms coats the silica structure. The surface He-3 is in fast exchange with the liquid on NMR time scales. The exchange coupling of liquid He-3 quasiparticles with the localized He-3 spins modifies the scattering of He-3 quasiparticles by the aerogel structure. In a magnetic field the polarization of the solid spins gives rise to a splitting of the scattering cross section of for "up" vs "down" spin quasiparticles, relative to the polarization of the solid He-3. We discuss this effect, as well as the effects of nonmagnetic scattering, in the context of a possible splitting of the superfluid transition for up arrowup arrow vs down arrowdown arrow Cooper pairs for superfluid He-3 in aerogel, analogous to the A(1)-A(2) splitting in bulk He-3. Comparison with the existing measurements of T-c for B<5 kG, which shows no evidence of the A(1)-A(2) splitting, suggests a liquid-solid exchange coupling of order Jsimilar or equal to0.1 mK. Measurements at higher fields, Bgreater than or similar to20 kG, should saturate the polarization of the solid He-3 and reveal the A(1)-A(2) splitting.