Interactions of soft atomic potentials and universality of low-temperature properties of glasses

It is shown that the interaction between soft atomic potentials in glasses leads to a density of the low-energy tunneling states, P{}, which does not depend on the concentration of defects. The dimensionless parameter P{}γ²/{ρ}v² which characterizes the interaction between two-level systems is estimated. It appears to be small in accordance with available experimental data. The theory developed allows us to understand both the insensitivity of low-temperature properties of glasses to the concentration of the defects (e.g., created by neutron irradiation) and the relatively small interaction between two-level systems. Making use of only three macroscopic material parameters, namely the mass density {ρ}, the sound velocity v, and the average value of the atomic mass M{}, nearly correct values are obtained for the two-level systems' density of states P{}, for the deformation potential {γ} and for other parameters describing the low-temperature properties of glasses. All of them appeared to be nearly the same for glassy systems. Thereby, the explanation of universality of the low-temperature properties of glasses is given.