One-Dimensional State and Superfluidity of ⁴He Nanotubes

Abstract

⁴He Bose fluids from three-dimensional (3D) to 1D states have been realized by using nanopores and flat substrates. The ⁴He films formed in the 3D nanopores show a 3D superfluid transition. The ⁴He fluids in the lower dimensions show superfluidity depending on measurement frequencies and system sizes. In the 2D films, superfluidity was observed at extremely high measurement frequencies in the normal fluid state above the Kosterlitz-Thouless transition temperature. The ⁴He nanotubes formed in 1D nanopores set in the 1D phonon state and show the superfluidity. The 2π-phase winding in the scale of the 1D length and "phase slip" play the main roles for the observation of superfluidity in the 1D state.