Elastic Properties of Solid 4He Monolayers from 4.2°K Vapor Pressure Studies
Heat capacity studies of monolayer 4He on exfoliated graphite have revealed a striking variety of surface-phase equilibria.1–4 In some cases the thermal behavior of these thin films has led to a direct comparison with the properties of the bulk. One of the most intriguing observations has been the near identity of the Debye temperatures at the same interatomic separation in the respective solid phases. This apparent coincidence has motivated the present study of those mechanical properties that determine the Debye θ at low temperature. In particular, how are the elastic constants for submonolayer solid helium related to those of the bulk? This question seems fundamental for eventual understanding of why the composite thermal behavior is analogous in two and three dimensions.
KeywordsEntropy Graphite Carbide Helium Compressibility
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