Role of Substrate Symmetry in Nucleating Solid Helium

Abstract

The continuous nucleation of bcc solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ from the liquid phase due to the presence of a MgO substrate is detected. For superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ there is no evidence of continuous nucleation of either the hcp or the bcc solid from the substrate. The experiment contrasts the influence of the square lattice of MgO with the triangular lattice of a basal-plane graphite substrate. The phenomenon of pore condensation for solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is discussed.