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Superflow in Solid 4He

Wayne M. Saslow
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Abstract

Kim and Chan have recently observed Non-Classical Rotational Inertia (NCRI) for solid $^4$He in Vycor glass, gold film, and bulk. Their low $T$ value of the superfluid fraction, $ρ_{s}/ρ\approx0.015$, is consistent with what is known of the atomic delocalization in this quantum solid. By including a lattice mass density $ρ_{L}$ distinct from the normal fluid density $ρ_{n}$, we argue that $ρ_{s}(T)\approxρ_{s}(0)-ρ_{n}(T)$, and we develop a model for the normal fluid density $ρ_{n}$ with contributions from longitudinal phonons and ``defectons'' (which dominate). The Bose-Einstein Condensation (BEC) and macroscopic phase inferred from NCRI implies quantum vortex lines and quantum vortex rings, which may explain the unusually low critical velocity and certain hysteretic phenomena.

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Wayne M. Saslow. 2004-07-07. Superflow in Solid 4He. https://doi.org/10.1103/physrevb.71.092502

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