CMT112

Impurity Effects on the A₁-A₂ Splitting of Superfluid ³He in Aerogel

• Author(s): J. A. Sauls^1,2 and Priya Sharma¹
• Address: ¹Department of Physics & Astronomy, Northwestern University, Evanston, IL 60208 USA
• Address: ²Centre de Recherches sur les Très Basses Températures, Centre National de la Recherche Scientifique, Laboratoire Associé à l'Université Joseph Fourier, Grenoble, France
• Date: June 4, 2003
• Journal: Physical Review B 68, 224502 (2003) [DOI] [PDF]
• Abstract: When liquid ³He is impregnated into silica aerogel a solid-like layer of ³He atoms coats the silica structure. The surface ³He is in fast exchange with the liquid on NMR timescales. The exchange coupling of liquid ³He quasiparticles with the localized ³He spins modifies the scattering of ³He 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 `up' vs. `down' spin quasiparticles, relative to the polarization of the solid ³He. We discuss this effect, as well as the effects of non-magnetic scattering, in the context of a possible splitting of the superfluid transition for ⇈ vs. ⇊ Cooper pairs for superfluid ³He in aerogel, analogous to the A₁-A₂ splitting in bulk ³He. Comparison with the existing measurements of T_c for B < 5 kG, which show no evidence of an A₁-A₂ splitting, suggests a liquid-solid exchange coupling of order J = 0.1 mK. Measurements at higher fields, B > 20 kG, should saturate the polarization of the solid ³He and reveal the A₁-A₂ splitting.

• Comment: 7 pages, 3 figures

• Eprint: [PDF] [arXiv]

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