Thermal transport in glassy selenium: The role of low-frequency librations

The experimental curves giving the temperature dependence of the thermal conductivity of glassy selenium are considered in detail. The observed behavior can be taken into account quantitatively if the densities of states for short-wavelength phonons as well as for low-energy librations arising from computer simulations are used for the calculations. In particular, it is shown that the lowest frequency excitations of a chain of selenium atoms can give due account of the plateau observed at temperatures about 2--10 K. The implications of the present findings for the current debate regarding the mechanisms for thermal transport in glasses are finally discussed.