Localized Bose-Einstein condensation in disordered liquid films
Phys. Rev. B 91, 094201 – Published 3 March, 2015
DOI: https://doi.org/10.1103/PhysRevB.91.094201
Abstract
We present neutron scattering measurements of the phonon-roton and layer modes of liquid helium films adsorbed in 25-Å 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 in porous media is an example of a Bose liquid in disorder. The existence of P-R modes above suggests the existence of patches or islands of Bose condensed liquid that have order [localized Bose-Einstein condensation (LBEC)] above . 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).