| Autor: |
M. Collins, E. Krotscheck, Glenn Agnolet, W. M. Saslow |
| Rok vydání: |
1993 |
| Předmět: |
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| Zdroj: |
Physical review. B, Condensed matter. 47(14) |
| ISSN: |
0163-1829 |
| Popis: |
Torsional-oscillator studies of very thin $^{4}\mathrm{He}$ films have found nonuniversal behavior of the superfluid response as a function of coverage. The temperature width of the superfluid transition region is nonmonotonic in the areal density n and exhibits cusplike variations at half of the layering period. We explore the assumption that this additional broadening is caused by macroscopic inhomogeneities in the substrate potential; such a theory for inhomogeneous broadening can be constructed from the Kosterlitz-Nelson relation between the superfluid areal density ${\mathit{n}}_{\mathit{s}}$ and the transition temperature ${\mathit{T}}_{\mathit{c}}$ by determining the theoretical ``sensitivity'' S of ${\mathit{n}}_{\mathit{s}}$ to variations in the strength of the substrate potential. For substrate models that are atomically uniform, a simple microscopic hypernetted-chain calculation (without either ``elementary diagrams'' or three-body correlations, but with an optimized Jastrow function) finds this sensitivity always to be of the same sign, and yields reasonable order-of-magnitude agreement with experiment. However, models for which the sensitivity does not change sign appear to be incapable of yielding either the cusps or the half-periodicity of the data. We suggest that these properties may occur with a more recently developed (and more sophisticated) version of hypernetted-chain theory, wherein ``elementary diagrams'' and three-body correlations are incorporated. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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