Anomalous Suppression of Superfluidity in ${}^4$He Confined in a Nano-porous Glass: Possible Quantum Phase Transition

Abstract

We explore superfluidity for ${}^4$He confined in a porous glass which has nanopores of 2.5 nm in diameter, at pressures up to 5 MPa. With increasing pressure, the superfluidity is drastically suppressed, and the superfluid transition temperature approaches 0 K at $P_c=3.5$ MPa. The features strongly suggest that the extreme confinement of ${}^4$He into the nanopores induces a quantum phase transition from superfluid to nonsuperfluid at 0 K, and at $P_c$.

4 pages, 4 figures, submitted to Physical Review Letters