Localized Bose-Einstein condensation in disordered liquid He-4 films

Article

关键词: POROUS VYCOR GLASS;    SUPERFLUID TRANSITION;    HE-4 FILMS;    COLLECTIVE EXCITATIONS;    TEMPERATURE-DEPENDENCE;    DENSITY-DEPENDENCE;    2-DIMENSIONAL HE-4;    HELIUM;    ROTON;    MEDIA;   

DOI  :  10.1103/PhysRevB.91.094201

来源: SCIE

【 摘 要 】

We present neutron scattering measurements of the phonon-roton and layer modes of liquid helium films adsorbed in 25-angstrom pore diameter gelsil as a function of temperature. The goal is to determine whether the well-defined phonon-roton and layer modes observed at low temperature at partial fillings of the porous media persist as well-defined modes at higher temperatures above the superfluid phase, as is the case of fully filled pores (3D liquid). We find that well defined P-R modes exist in films at temperatures well above the superfluid phase. This is the case at all fillings investigated. Liquid He-4 in porous media is an example of a Bose liquid in disorder. The existence of P-R modes above T-c suggests the existence of patches or islands of Bose condensed liquid that have order [localized Bose-Einstein condensation (LBEC)] above T-c. The interpretation is that the well-defined P-R modes propagate in the patches of BEC. Gelsil partially filled with liquid helium shows the same LBEC behavior as found previously in fully filled gelsil (as in a 3D liquid).

【 授权许可】

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