Liquid-Solid Transition and Phase Diagram of ^4He Confined in Nanoporous Glass

摘要

We have studied the liquid - solid (L-S) phase transition of ^4He confined innanoporous glass, which has interconnected nanopores of 2.5 nm in diameter. TheL-S boundary is determined by the measurements of pressure and thermal responseduring slow cooling and warming. Below 1 K, the freezing pressure is elevatedto 1.2 MPa from the bulk freezing pressure, and appears to be independent oftemperature. The T-independent L-S boundary implies the existence of alocalized Bose-Einstein condensation state, in which long-range superfluidcoherence is destroyed by narrowness of the nanopores and random potential.