Hysteresis of Low-Temperature Thermal Conductivity and Boson Peak in Glassy (g) AsS: Nanocluster Contribution.

Experimental results of the thermal conductivity (k(T)) of nanostructured g-AsS during cooling and heating processes within the temperature range from 2.5 to 100 K have been analysed. The paper has considered thermal conductivity is weakly temperature k(T) dependent from 2.5 to 100 K showing a plateau in region from 3.6 to 10.7 K during both cooling and heating regimes. This paper is the first attempt to consider the k(T) hysteresis above plateau while heating in the range of temperature from 11 to 60 K. The results obtained have not been reported yet in the scientific literature. Differential curve Δk(T) of k(T) (heating k(T) curve minus cooling k(T) curve) possesses a complex asymmetric peak in the energy range from 1 to 10 meV. Δk(T) reproduces the density of states in a g(ω)/ω representation estimated from a boson peak experimentally obtained by Raman measurement within the range of low and room temperatures. Theoretical and experimental spectroscopic studies have confirmed a glassy structure of g-AsS in cluster approximation. The origin of the low-frequency excitations resulted from a rich variety of vibrational properties. The nanocluster vibrations can be created by disorder on atomic scale.