Bose-Einstein Condensation Measurements and Superflow in Condensed Helium
| Autor: | Henry R. Glyde |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
Condensed Matter::Quantum Gases
Materials science Bose gas Condensed Matter::Other Vapor pressure Condensation chemistry.chemical_element Condensed Matter Physics Atomic and Molecular Physics and Optics Amorphous solid law.invention chemistry law General Materials Science Atomic physics Porous medium Bose–Einstein condensate Helium Bar (unit) |
| Zdroj: | Journal of Low Temperature Physics. 172:364-387 |
| ISSN: | 1573-7357 0022-2291 |
| Popis: | We review the formulation and measurement of Bose-Einstein condensation (BEC) in liquid and solid helium. BEC is defined for a Bose gas and subsequently for interacting systems via the one-body density matrix (OBDM) valid for both uniform and non-uniform systems. The connection between the phase coherence created by BEC and superflow is made. Recent measurements show that the condensate fraction in liquid 4He drops from 7.25±0.75 % at saturated vapor pressure (p≈0) to 2.8±0.2 % at pressure p=24 bars near the solidification pressure (p=25.3 bar). Extrapolation to solid densities suggests a condensate fraction in the solid of 1 % or less, assuming a frozen liquid structure such as an amorphous solid. Measurements in the crystalline solid have not been able to detect a condensate with an upper limit set at n 0≤0.3 %. Opportunities to observe BEC directly in liquid 4He confined in porous media, where BEC is localized to patches by disorder, and in amorphous solid helium is discussed. |
| Databáze: | OpenAIRE |
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