Superfluidity of ${}^4$He Confined in Nano-Porous Media

Abstract

We have examined superfluid properties of ${}^4$He confined to a nano-porous Gelsil glass that has nanopores 2.5 nm in diameter. The pressure-temperature phase diagram was determined by torsional oscillator, heat capacity and pressure studies. The superfluid transition temperature $T_{\mathrm{c}}$ approaches zero at 3.4 MPa, indicating a novel "quantum" superfluid transition. By heat capacity measurements, the nonsuperfluid phase adjacent to the superfluid and solid phases is identified to be a nanometer-scale, localized Bose condensation state, in which global phase coherence is destroyed. At high pressures, the superfluid density has a $T$-linear term, and $T_{\mathrm{c}}$ is proportional to the zero-temperature superfluid density. These results strongly suggest that phase fluctuations in the superfluid order parameter play a dominant role on the phase diagram and superfluid properties.

6 Pages, 6 Figures, Submitted to "Helium: 100 years", Special Issue of Low Temperature Physics

Cited by in corpus (4)

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• ${}^4$He in Nanoporous Media: 4D XY Quantum Criticality at Finite Temperatures