Phonons, rotons, and localized Bose-Einstein condensation in liquid He4 confined in nanoporous FSM-16
| Autor: | Henry R. Glyde, Jacques Bossy, Jacques Ollivier |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Condensed Matter::Quantum Gases
Physics Condensed matter physics Condensed Matter::Other Phonon Vapor pressure Transition temperature 02 engineering and technology Neutron scattering Atmospheric temperature range 021001 nanoscience & nanotechnology 01 natural sciences Superfluidity 0103 physical sciences 010306 general physics 0210 nano-technology Intensity (heat transfer) Energy (signal processing) |
| Zdroj: | Physical Review B. 99 |
| ISSN: | 2469-9969 2469-9950 |
| DOI: | 10.1103/physrevb.99.165425 |
| Popis: | We present neutron scattering measurements of the phonon-roton and layer modes of liquid helium confined in 28 \AA{} diameter nanopores of FSM-16. The goal is to determine the energy, lifetime, and intensity of the modes as a function of temperature. It is particularly to determine the highest temperature, denoted ${T}_{PR}$, at which well-defined phonon-roton modes are observed at higher wave vector ($Qg0.8$ ${\AA{}}^{\ensuremath{-}1}$) in the nanopores. The temperature ${T}_{PR}$, which can be identified with loss of Bose-Einstein condensation (BEC), can be compared with the superfluid to normal liquid transition temperature, ${T}_{O}$, and other transition temperatures of $^{4}\mathrm{He}$ in the nanopores. The aim is to identify the nature of BEC in a narrow nanopore. Two pressures are investigated, saturated vapor pressure (SVP) and $p=26$ bars. We find that well-defined P-R modes are observed up to temperatures much higher than the conventional superfluid to normal liquid transition temperature, ${T}_{O}$, observed in torsional oscillator measurements, i.e., ${T}_{PR}g{T}_{O}$. At SVP, ${T}_{PR}=1.8$ K and ${T}_{O}=0.9$ K. This supports the interpretation that BEC exists in a localized or partially localized form in the temperature range ${T}_{O}lTl{T}_{PR}$; i.e., there is a localized BEC region lying between the superfluid and fully normal liquid phase, as observed in some other porous media. At close to full filling, the P-R mode energies in FSM-16 are similar to those in bulk liquid $^{4}\mathrm{He}$. However, a substantial P-R mode width at $T\ensuremath{\rightarrow}0$ K and at higher temperatures is observed. |
| Databáze: | OpenAIRE |
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