This paper reviews recent findings of novel phenomena in 4He confined to a nano-porous glass. We examined pressure-temperature (P-T) phase diagram of 4He confined in a porous Gelsil glass that had nanopores 2.5 nm in diameter, by torsional oscillator and pressure studies. The obtained phase diagram is fairly unprecedented: the superfluid transition temperature approaches zero at 3.4 MPa, and a novel nonsuperfluid phase exists between the superfluid and solid phase. These observations indicate that the confined 4He undergoes a superfluid-nonsuperfluid-solid quantum phase transition at zero temperature. We propose that the nonsuperfluid phase may be a localized Bose-condensed state in which global phase coherence is destroyed by a strong correlation between the 4He atoms or by a random potential. 4He in nanospace is an excellent model system for studying a strongly correlated Bose liquid and solid in a confinement potential.
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