A Semiquantum Liquid and a New Ordered Phase of ⁴He Adsorbed in Y Zeolite

Abstract

A fluidity and a quantum effect of a new helium 4 system, unsaturated ⁴He adsorbed in a narrow void channel of Y-zeolite crystal, have been studied by measuring the heat capacity. In the case of the quantity adsorbed n=0.445×10⁻³ mol/g, the heat capacity C is proportional to the temperature, i.e. C=nαT, in the condition T_c (=3.25 K)≤T\lesssim9 K, and it reduces suddenly below T_c. The coefficient α is 2.2 J/K²/mol. The experimental result shows that the state above T_c is a semiquantum liquid such as bulk ⁴He which remains liquid to much lower temperatures than the Debye temperature. Below T_c, the result indicates the presence of an ordered state.