Possible Ising Transition in aHe4Monolayer Adsorbed on Kr-Plated Graphite

Abstract

The specific heat of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ adsorbed on Kr-plated graphite indicates the existence of an order-disorder transition from a (1×1) [½] triangular structure on a honeycomb lattice of adsorption sites. The specific heat singularity is logarithmic, as predicted from universality considerations, different from the power law observed in the $(\sqrt{3}\times \sqrt{3})R30\mathrm{}°$ order-disorder transition of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ on the bare graphite.