Low Temperature Physics: 34, 273 (2008); https://doi.org/10.1063/1.2908885 (6 pages)
Физика Низких Температур: Том 34, Выпуск 4-5 (Апрель 2008), c. 350-356    ( к оглавлению , назад )

Superfluidity of 4He confined in nanoporous media

Keiya Shirahama, Keiichi Yamamoto, and Yoshiyuki Shibayama

Department of Physics, Keio University, Yokohama 223-8522, Japan
E-mail: keiya@rk.phys.keio.ac.jp

Received December 5, 2007


We have examined superfluid properties of 4He confined to a nanoporous 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 Tc 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 Tc 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.

PACS: 67.25.D– Superfluid phase;
PACS: 81.07.–b Nanoscale materials and structures: fabrication and characterization.

Key words: nanoporous glass, torsional oscillator, superfluid transition.