OBSERVATION OF SUPERFLUID HE-4 ADSORBED IN ONE-DIMENSIONAL MESOPORES

To study one-dimensional (1D) quantum liquid of He-4, we measured the heat capacity and performed a torsional oscillator experiment for He-4 adsorbed on a new mesoporous substrate whose adsorption area consists of walls of straight one-dimensional 18 Angstrom diameter tunnels. Th e presence of adsorbed quantum liquid was examined by the isotope effe ct on the heat capacity for He-3 and He-4 adatoms. Above a coverage n( o), the heat capacity isotherms are completely different because of th e Fermi and the Bose fluids, respectively. In the torsional oscillator experiment we observed superfluid He-4 above n(o). The fraction of th e superfluid decoupled from the motion of the substrate is 0.13, which is the same order as 0.18 for packed Pt fine powder and 0.24 for 80 A ngstrom-porous glasses. The result indicates that the superfluid state exists in the one-dimensional He-4 adatoms formed in the 18 Angstrom diameter pores.