Surface-dominated finite size effects in nanoconfined superfluid helium

Abstract

Superfluid ${}^4$He (He-II) is a widely studied model system for exploring finite-size effects in strongly confined geometries. Here, we study He-II confined in mm-scale channels of 25 and 50 nm height at high pressures using a nanofluidic Helmholtz resonator. We find that the superfluid density is measurably suppressed in the confined geometry from the transition temperature down to 0.6 K. Importantly, this suppression can be accounted for by roton-like thermal excitation with an energy gap of 5 K. We show that the surface-bound excitations lead to the previously unexplained lack of finite-size scaling of suppression of the superfluid density.

Version 2: 14 pages (5 + 9 supplemental material; 3 + 10 figures). Accepted to Phys. Rev. Lett

References in corpus (6)

• The dispersion relation of Landau elementary excitations and the thermodynamic properties of superfluid ${}^4$He
• Thermodynamic Evidence for Nanoscale Bose-Einstein Condensation in ^4He Confined in Nanoporous Media
• Superfluid nanomechanical resonator for quantum nanofluidics
• Triangular pair density wave in confined superfluid ${}^3$He
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