Localized Bose-Einstein Condensation of ^4He Confined in Nanoporous Media(<Special Topics>New Frontiers of Quantum Fluids and Solids)

概要

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^4He confined in nanoporous media is an excellent model boson system in a confinement potential. We have studied the superfluid and thermodynamic properties of ^4He confined in a porous glass that has nanopores of 2.5nm diameter. It is shown that the confinement of ^4He in nanopores produces a new quantum state, the localized Bose-Einstein condensation (LBEC) state, and markedly alters the pressure-temperature (P-T) phase diagram. In the LBEC state the global phase coherence is destroyed by strong atomic correlation or by the random potential of a substrate. The formation of LBEC leads to an anomalous reduction of the superfluid transition temperature T_c determined by the torsional oscillator technique, and the behavior of a quantum phase transition near 0K. The contributions of roton and phonon excitations to the heat capacity provide definitive evidence of the LBEC state.
社団法人日本物理学会の論文
2008-11-15