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arXiv · 0712.1153

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

Keiya Shirahama·Keiichi Yamamoto·Yoshiyuki Shibayama
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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.

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Keiya Shirahama, Keiichi Yamamoto, Yoshiyuki Shibayama. 2007-12-07. Superfluidity of $^4$He Confined in Nano-Porous Media. https://doi.org/10.1063/1.2908885

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