Modification of the Low-Density Phases of Adsorbed Helium Monolayer Films Produced by Changes in the Adsorbing Substrate

Abstract

The specific heats of monolayer ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ films adsorbed on Ar-plated Grafoil show prodound differences from films on bare Grafoil. The apparent liquefaction temperature of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is doubled, and the interacting Fermi gas behavior of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is modified to show either condensation or strong band effects.